Calculators
Everyday sums, money, dates and timers.
Money
Percentage CalculatorWhat is X% of Y, X is what % of Y, and percentage change.Tip CalculatorWork out the tip and split the bill between any number of people.Discount CalculatorWhat you pay after a discount, and what you actually saved.VAT & Sales TaxAdd or remove VAT, GST or sales tax at any rate.Loan CalculatorMonthly repayments, total interest and a full amortisation schedule.Compound InterestWatch savings grow with monthly deposits and compound interest.Savings GoalHow long to reach a target — or how much per month — interest included.Rent Split CalculatorFair rent shares — equal, by income, or by room size, honestly argued.Fuel Cost CalculatorThe cost of a trip from distance, consumption and fuel price.Electricity CostWhat an appliance costs to run per day, month and year.Invoice GeneratorRemembers your details, logo and clients. Print a clean PDF.Time TrackerClock in and out on projects and see your hours add up by day and week.Salary ConverterHourly to yearly to monthly — type any figure and the rest follow.Margin CalculatorCost, price, margin and markup — any two in, the confusion settled.Overtime PayTime-and-a-half and double time, itemised into a gross weekly total.Unit Price CalculatorCompare products by price per 100 g, 100 ml or item — find the best value.Mortgage CalculatorMonthly payment, total interest, amortisation schedule and overpayment savings.Expense SplitterWho paid what on the trip — and the fewest transfers to settle up.Quotation GeneratorLine-item quotes with tax, validity and notes — print or save as PDF.Expense Report GeneratorItemised expense claims by category with receipt ticks and CSV export.Mileage LogLog business trips, apply a per-mile rate and export the claim as CSV.Budget PlannerMonthly budget by needs, wants and savings with the 50/30/20 check.Subscription TrackerEvery recurring bill in one list, with the true monthly and yearly cost.Credit Card Payoff CalculatorMonths and interest to clear a balance at a fixed or minimum payment.Net Worth CalculatorAssets minus liabilities with saved snapshots to track the trend.Debt Snowball CalculatorSnowball vs avalanche payoff plans: months, interest and debt-free date for every debt.Retirement CalculatorProject your pension pot to retirement age in today's money, plus the income it gives.Inflation CalculatorWhat an amount is worth between two years at a rate you set — purchasing power lost.Receipt GeneratorA till-style receipt for a payment received: items, tax and a PAID stamp. Print or PDF.Purchase Order GeneratorPO with number, supplier, ship-to, SKU lines, delivery date and terms. Print or PDF.ROI CalculatorReturn on investment and annualised ROI, comparing up to three investments.CAGR CalculatorCompound annual growth rate between two values, plus end value and years needed.NPV & IRR CalculatorNet present value, IRR, payback and profitability index from your cash flows.Timesheet CalculatorWeekly hours from start and end times with breaks, overtime rules and gross pay.Payslip GeneratorA printable pay statement with earnings, deductions, net pay and year-to-date.Rent vs Buy CalculatorYear-by-year net cost of owning versus renting, and the year buying pulls ahead.SIP CalculatorMonthly investment growth with step-up: invested, gains and maturity value.Stock Average CalculatorAverage cost per share across buys, profit or loss, and shares to reach a target.FD CalculatorFixed deposit maturity value with any compounding, tenure and yearly table.RD CalculatorRecurring deposit maturity from a monthly instalment, rate and tenure.Simple Interest CalculatorI = P × R × T — solve for interest, principal, rate or time, in days or years.APR CalculatorThe true annual rate of a loan once fees are included, plus effective annual rate.Home Affordability CalculatorHow much house you can afford from income, debts and deposit, by the 28/36 rule.Debt-to-Income CalculatorFront-end and back-end DTI ratios with the thresholds lenders use.Emergency Fund CalculatorHow big your emergency fund should be, the gap, and months to build it.FIRE CalculatorYour financial independence number, years to reach it, and Coast FIRE.Loan Comparison CalculatorCompare three loan offers: payment, interest, fees, total cost and APR.Dividend CalculatorDividend yield, monthly income and a DRIP reinvestment projection with growth.Crypto Profit CalculatorProfit, ROI and break-even price on a crypto trade after buy and sell fees.Car Lease vs Buy CalculatorNet cost of leasing a car against buying it with a loan, resale value included.Smoking Cost CalculatorWhat smoking or vaping costs a year and a decade, and savings since quitting.Pay Raise CalculatorNew salary from a raise, the percentage, per-period pay and real raise.Packing Slip GeneratorPrintable packing slips with ordered, shipped and back-ordered quantities.Rule of 72 CalculatorHow long money takes to double at a rate, or the rate to double in a set time.TVM CalculatorFinancial calculator: solve N, I/Y, PV, PMT or FV for loans and savings.Annuity CalculatorMonthly income a pot can pay for a set time, or the pot needed for an income.IRR CalculatorInternal rate of return, NPV, MIRR and profitability index for cash flows.Payback Period CalculatorSimple and discounted payback for even or uneven yearly cash flows.Bond Yield CalculatorYield to maturity and current yield from price, or price from a yield.Rental Property CalculatorCash flow, cap rate, cash-on-cash return and DSCR for a buy-to-let.Mortgage Points CalculatorAre discount points worth it? Cost, monthly saving and break-even month.Refinance CalculatorNew payment, monthly saving and break-even on closing costs when refinancing.Dollar-Cost Averaging CalculatorUnits bought, average cost and lump-sum comparison for regular investing.50/30/20 Budget CalculatorSplit take-home pay into needs, wants and savings, and compare with real spending.EV Charging Cost CalculatorCost, time and range of charging an electric car at home or a public charger.EV vs Petrol Cost CalculatorYearly running cost of an electric car vs petrol or diesel, payback and CO2.College Savings CalculatorProjected university cost and the monthly saving needed to reach it.Wedding Budget CalculatorSplit a wedding budget by category, cost per guest and track spending.Cash CounterCount notes and coins for a till or cash box, with float and over/short.Car Loan CalculatorMonthly payment, amount financed and interest with deposit, trade-in, tax and fees.Student Loan CalculatorUK income-contingent repayments and write-off, or a standard US-style loan.UK Income Tax CalculatorTake-home pay after income tax, National Insurance, pension and student loan.Stamp Duty CalculatorSDLT, Scottish LBTT and Welsh LTT with first-time buyer and second-home rates.Investment Fee CalculatorHow much fund and platform fees cost you over time, comparing two fee levels.Loan-to-Value CalculatorMortgage LTV %, your lender band and the deposit needed for each band.Late Payment Interest CalculatorUK statutory interest (8% + base rate) and compensation on overdue invoices.Rent Affordability CalculatorHow much rent you can afford: 30% rule, 40× landlord test and your budget.Cost Per Use CalculatorCompare purchases by the real cost of each use, including upkeep and resale.Sales Tax CalculatorAdd sales tax, remove it from a total, or find the rate — state plus local.Capital Gains Tax Calculator (UK)UK CGT on shares, crypto or property: £3,000 allowance, 18% and 24% rates.Inheritance Tax Calculator (UK)UK IHT on an estate: nil-rate bands, spouse transfers, charity 36% rate.Dividend Tax Calculator (UK)Tax on UK dividends on top of salary: £500 allowance, 8.75% to 39.35%.Self-Employed Tax Calculator (UK)Sole trader income tax and Class 4 NI from profit, with take-home pay.Marriage Allowance CalculatorCheck if you qualify for UK marriage allowance and how much you'd save.Offset Mortgage CalculatorInterest and years saved by offsetting savings against your mortgage.Pension Tax Relief CalculatorWhat a UK pension contribution really costs after tax relief and NI.State Pension Age CalculatorYour UK State Pension age and the exact date you reach it.Rent Increase CalculatorNew rent, percentage rise, yearly cost and start date after notice.Price per Square Foot CalculatorCompare properties by price per square foot and per square metre.Paycheck Calculator (US)US take-home pay per paycheck after federal, FICA, state tax and 401(k).401(k) CalculatorProject your 401(k) with employer match, raises, returns and IRS limits.Roth IRA CalculatorYour 2026 Roth IRA limit after the income phase-out, and tax-free growth.HSA Calculator2026 HSA limits, the tax you save and what an invested HSA could grow to.Balance Transfer CalculatorDoes a 0% balance transfer save money after the fee? Compare and see.APY CalculatorConvert APR to APY (AER) for any compounding, and see interest earned.Closing Cost CalculatorEstimate US home closing costs and the cash you need to close.Stock Profit CalculatorProfit, return, annualised return and break-even price on a stock trade.Options Profit CalculatorPayoff at expiry for calls and puts: break-even, max profit and loss.Sinking Fund CalculatorHow much to save each month for planned costs by their due dates.Car Depreciation CalculatorWhat a car will be worth year by year, and what depreciation costs per mile.Travel Budget CalculatorPlan trip costs per person and per day, with a contingency.
Business & marketing
Break-Even CalculatorUnits and revenue to cover fixed costs, with a chart and target profit.Ad Cost CalculatorCPM, CPC, CTR, CPA, ROAS and break-even ROAS from your campaign figures.A/B Test CalculatorIs the lift real? p-value, confidence interval and the sample size you need.Decision MatrixWeighted scoring of options against criteria, with a sensitivity check.Freelance Rate CalculatorThe hourly and day rate you need from income, costs, time off and billable share.Commission CalculatorFlat, tiered marginal or retroactive commission, with splits and base pay.Product Pricing CalculatorSolve the selling price for a target margin after materials, labour and marketplace fees.SaaS Metrics CalculatorMRR, ARR, churn, net revenue retention, LTV, CAC and payback from one month.Startup Runway CalculatorMonths of cash left, the zero-cash month and break-even with growth rates.Meeting Cost CalculatorWhat a meeting costs in salaries, with a live ticker and the yearly cost if recurring.Cash Flow ForecastTwelve months of money in and out with recurring lines, a chart and the low point.NPS CalculatorNet Promoter Score from counts or raw survey scores, with margin of error.Sample Size CalculatorSurvey responses needed for a confidence level and margin of error, and the reverse.Depreciation CalculatorStraight-line, declining balance, SYD and units-of-production schedules.Payment Terms CalculatorNet 30 / EOM due dates, 2/10 net 30 discount value and late interest.Reorder Point CalculatorWhen to reorder stock: lead-time demand plus safety stock from a service level.EOQ CalculatorEconomic order quantity, orders per year and total ordering + holding cost.Conversion Funnel CalculatorStep conversion rates, drop-off and traffic needed to hit a sales target.Inventory Turnover CalculatorInventory turnover ratio, days inventory outstanding and sell-through rate.SMART Goal GeneratorTurn a rough goal into a SMART goal statement with milestones and checks.SWOT AnalysisA printable SWOT grid with TOWS strategy prompts, saved as you type.RACI MatrixWho's responsible, accountable, consulted and informed — with checks and CSV.Business Model CanvasThe nine-block business model canvas online, printable and saved as you type.Buyer Persona GeneratorA one-page buyer persona: goals, pains, objections, channels and key message.Content CalendarPlan posts by date, channel and status in a month grid, then export CSV.Eisenhower MatrixSort tasks into Do, Schedule, Delegate and Delete by urgency and importance.Employee Cost CalculatorTrue yearly cost of an employee beyond salary, and cost per productive hour.Tip Pool CalculatorShare pooled tips by hours, role points or equally, with cash rounding.OKR GeneratorWrite Objectives and Key Results with quality checks and 0–1 scoring.PTO Accrual CalculatorPaid time off accrued per pay period or hours worked, and UK holiday pay.Notice Period CalculatorYour last day from the notice date and length, plus UK statutory notice.Equity Dilution CalculatorHow a funding round and option pool dilute founders and shareholders.Startup Valuation CalculatorRevenue multiple, VC method and Scorecard valuations side by side.COGS CalculatorCost of goods sold, gross margin, inventory turnover and unit costs.PERT Estimate CalculatorThree-point task estimates with project totals and confidence levels.RICE Score CalculatorPrioritise features by Reach, Impact, Confidence and Effort.Job Offer Comparison CalculatorCompare offers on total pay, benefits, costs, living costs and hours.Employee Turnover CalculatorTurnover and retention rates, voluntary vs involuntary, and the cost.Bradford Factor CalculatorAbsence score S² × D from spells and days or a list of dates.FTE CalculatorFull-time equivalent, pro-rata salary and holiday for part-time staff.Utilization Rate CalculatorBillable vs available hours for a person or team, against a target.Job Application TrackerTrack applications by stage with follow-up dates, response rate and CSV export.
Dates, age & pets
Age CalculatorYour exact age in years, months, days — plus the next birthday.Date CalculatorDays between two dates, or add and subtract days from one.Days SinceLive day counts since any date — anniversaries, streaks, milestones.Day of the WeekWhat day any date falls on — including the day you were born.CalendarBrowse any month and year, with week numbers — and print it.Working Days CalculatorBusiness days between dates, or a deadline N working days from now.Week NumberWhat week is it? Today's ISO week number and every week of the year.Leap Year CheckerIs any year a leap year? The full rule, explained, with the next five.Easter CalculatorThe exact date of Easter for any year — plus Lent, Pentecost and Pancake Day.Moon PhaseTonight's moon phase, any date's, and the next full and new moons.Sunrise & SunsetSun times for any place and date — NOAA math, computed on your device.Zodiac Sign FinderYour star sign from your birth date — plus your Chinese zodiac animal.Christmas CountdownDays, hours and sleeps until Christmas — live, in your time zone.New Year CountdownLive countdown to midnight, January 1 — plus how much of the year is left.Dog Age CalculatorYour dog's age in human years, adjusted for size.Cat Age CalculatorYour cat's age in human years, on the chart vets use.Age Difference CalculatorExact age gap between two birth dates in years, months, days and total days.Life in WeeksYour life as a grid of weeks, with weeks lived and left and upcoming milestones.Baby Age CalculatorBaby's age in months, weeks and days, corrected age for preemies, and milestones.Pet Calorie CalculatorDaily calories and food portions for a dog or cat by weight and life stage.Generation CalculatorWhich generation you belong to by birth year, from Boomers to Gen Beta.Calendar ConverterA date in the Hebrew, Islamic, Persian, Chinese, Julian and other calendars.Julian Date ConverterDate ↔ day of year (YYDDD) for food codes, plus astronomical JD and MJD.Dog Chocolate Toxicity CalculatorTheobromine dose in mg/kg from chocolate type, amount and dog weight.Half Birthday CalculatorFind your half birthday, how many days until it and your 'and a half' age.School Year CalculatorWhich school year or grade a child is in from their birthday, UK and US.Wedding Anniversary CalculatorYears married, next anniversary, gift by year and day milestones.
Clocks & time zones
World ClockThe current time in cities around the world, all at once.Time Zone ConverterCompare a time across cities and find a slot that works for everyone.Digital ClockA big, clear clock for a second screen — full screen, any time zone.Analog ClockA classic clock face with sweeping hands, in any time zone.Binary ClockThe classic BCD clock — read the time from lights, learn binary free.Alarm ClockSet an alarm for any time of day and it rings, even in a background tab.Meeting PlannerFind an hour inside everyone's working day across up to eight time zones.Military Time ConverterConvert 12-hour and 24-hour time, how to say it, and a full chart.Jet Lag CalculatorTime zones crossed, adjustment time and a light and sleep plan.
Timers
Timer & StopwatchA countdown timer with an alarm, and a stopwatch with laps.StopwatchA big, precise stopwatch with lap times — space bar to start.Countdown to a DateA live countdown to any date — days, hours, minutes and seconds.Pomodoro TimerWork for 25, break for 5 — with automatic cycles and a session count.Interval TimerA HIIT and Tabata timer — work, rest, rounds, big colours and beeps.Egg TimerSoft, medium or hard — pick your yolk, get a countdown and alarm.Time CalculatorAdd and subtract hours, minutes, seconds — plus decimal hours.Meeting TimerAgenda items with minutes, a big countdown, round-robin speakers, overrun tally.Contraction TimerTime labour contractions: length, frequency and a 5-1-1 check.Breathing ExerciseGuided breathing: box breathing, 4-7-8 and resonant breathing with an animation.Meditation TimerA quiet meditation timer with singing-bowl bells and interval chimes.
School & science
Scientific CalculatorTrig, logs, powers and parentheses, with a visible history.GPA CalculatorWork out your GPA from letter grades and credit hours.Final Grade CalculatorWhat do you need on the final to hit your target grade?Times TablesThe multiplication grid, plus a practice quiz that keeps score.FlashcardsMake flashcard decks and quiz yourself — flip, shuffle and track what you know.Sig Figs CalculatorCount significant figures with the rule that applied, and round to any.Scientific NotationDecimal to a × 10ⁿ and back — with e-notation and engineering form.Periodic TableAll 118 elements by category, with search and atomic weights.Molar Mass CalculatorMolar mass and mass percent from a chemical formula, with grams ↔ moles.Matrix CalculatorDeterminant, inverse, rank, multiply and solve Ax = b, in exact fractions.Permutation & Combination CalculatornPr and nCr with and without repetition, exact for any size, with listings.Graphing CalculatorPlot up to four functions of x with pan, zoom and trace — no sign-up.Attendance CalculatorAttendance %, classes to attend to reach 75%, and how many you can miss.Half-Life CalculatorExponential decay: amount left, time, half-life or start, with isotopes.Dilution CalculatorC1V1 = C2V2 for any unknown, with units, mixing amounts and serial dilutions.pH CalculatorpH, pOH, [H⁺] and [OH⁻]; strong and weak acids and bases; buffers.SUVAT CalculatorConstant-acceleration motion: give any three of s, u, v, a, t, get the rest.Percent Error CalculatorPercent error, signed and absolute error, and percent difference, with working.Density CalculatorSolve density, mass or volume with units, and compare with common materials.Molarity CalculatorMass to weigh, molarity or volume for a solution, with compound presets.Ideal Gas Law CalculatorSolve PV = nRT for pressure, volume, moles or temperature in any units.Projectile Motion CalculatorRange, max height, flight time and impact speed with a trajectory plot.Wavelength & Frequency CalculatorConvert wavelength and frequency for light or sound, with photon energy.Weight on Other PlanetsYour weight and jump height on the Moon, Mars, Jupiter and beyond.Energy CalculatorKinetic and potential energy, power, and joules to kWh, kcal and BTU.Long Division CalculatorLong division with every step shown, remainder and repeating decimals.Maths Worksheet GeneratorPrintable arithmetic worksheets with answer keys for any number range.Chemical Equation BalancerBalance any chemical equation exactly, with brackets, hydrates and charges.Empirical Formula CalculatorEmpirical and molecular formula from percent composition or masses.Punnett Square CalculatorMono-, di- and trihybrid crosses with genotype and phenotype ratios.Blood Type CalculatorPossible child blood types (ABO and Rh) from the parents' blood types.DNA TranslatorComplement, reverse complement, mRNA and protein in three reading frames.Unit CircleInteractive unit circle with sin, cos, tan and exact values for every angle.Greek AlphabetAll 24 Greek letters with names, pronunciation and uses — click to copy.Test Grade CalculatorTest score percentage and letter grade, plus a printable grading chart.Rubric MakerBuild, score and print a grading rubric with criteria and levels.Simultaneous Equations SolverSolve 2–4 linear equations exactly, with fractions, checks and steps.Age on Other PlanetsYour age in Mercury, Mars, Jupiter and other planet years, and next birthdays.Air Density CalculatorAir density from temperature, pressure or altitude and humidity.Beaufort Scale ConverterWind speed to Beaufort force 0–12 with land and sea effects.Lightning Distance CalculatorHow far away lightning struck, from flash-to-thunder seconds.Earthquake Magnitude CalculatorCompare earthquake magnitudes: shaking, energy and TNT equivalent.Speed of Sound CalculatorSpeed of sound at any temperature, in water and solids, with wavelength.Free Fall CalculatorFall time and impact speed, with or without air resistance.Momentum CalculatorMomentum, impulse and elastic or inelastic collisions.Force CalculatorF = ma in any units, plus the resultant of several forces.Hooke's Law CalculatorSpring force, constant, energy, period and springs combined.Gravitational Force CalculatorNewton's law of gravitation between any two masses.Pendulum CalculatorPendulum period, frequency and length, with large-swing correction.Centripetal Force CalculatorCentripetal force, acceleration, g-force and banking angle.Buoyancy CalculatorBuoyant force, float or sink, and how much is submerged.Inclined Plane CalculatorForces on a slope with friction: sliding, acceleration, effort.Escape Velocity CalculatorEscape and orbital speed for any planet, moon or star.Orbital Period CalculatorOrbit period and speed from altitude (Kepler's third law).Light-Year ConverterConvert light-years, parsecs, AU, km and miles, with travel times.Time Dilation CalculatorRelativistic time dilation for speed and gravity, with GPS.Doppler Effect CalculatorDoppler shift for sound and light, with redshift z.Lens Equation CalculatorThin lens and mirror equation: image distance and magnification.Snell's Law CalculatorRefraction angle, critical angle and Brewster's angle.Specific Heat CalculatorQ = mcΔT: heat energy, mass, specific heat or temperature change.Percent Yield CalculatorPercent yield and theoretical yield from the limiting reactant.Thermal Expansion CalculatorLinear and volume thermal expansion of solids and liquids.Sun Angle CalculatorSun elevation, azimuth and shadow length for any place and time.Boiling Point at AltitudeThe temperature water boils at for any altitude or air pressure.Handwriting Worksheet GeneratorPrintable tracing sheets for letters, words and sentences.Report Card Comment GeneratorDraft personalised report card comments from strengths and next steps.Lesson Plan GeneratorFill in and print a structured lesson plan with a timing check.Spelling Test MakerPrintable spelling tests, practice grids and word puzzles.Number Line GeneratorPrintable number lines with decimals, negatives or fractions.Clock Worksheet GeneratorPrintable telling-time worksheets with an answer key.Study PlannerRevision timetable from your exams, hours and subjects.
Maths & geometry
Fraction CalculatorAdd, subtract, multiply and divide fractions, with the steps shown.Ratio CalculatorSolve a:b = c:d for the missing value, and simplify any ratio.Average CalculatorMean, median, mode, range and sum from any list of numbers.Standard DeviationSample or population standard deviation with every step shown.Quadratic SolverRoots, discriminant and vertex for ax² + bx + c — complex roots included.Prime NumbersCheck if a number is prime, factorise it, and list primes to 100,000.GCD & LCMGreatest common divisor and least common multiple, with Euclid's steps.Area CalculatorRectangle, circle, triangle, trapezoid and ellipse — area and perimeter.Volume CalculatorBox, sphere, cylinder, cone and pyramid volumes — litres included.Slope CalculatorTwo points in — slope, line equation, intercepts, distance, midpoint out.Pythagorean TheoremSolve any side of a right triangle, drawn to scale, working shown.Speed Distance TimeEnter any two, get the third — km/h, mph, m/s and knots handled.Triangle SolverSolve any triangle from three values: sides, angles, area, heights and type.Logarithm CalculatorLog to any base, natural log, antilog and solving for the base, with rules.Z-Score CalculatorZ-scores, percentiles and p-values, and z from a percentile, with a bell curve.Linear Regression CalculatorLine of best fit from x, y data: slope, intercept, r, R² and a scatter plot.Confidence Interval CalculatorConfidence intervals for a mean (t or z) or a proportion (Wilson).Truth Table GeneratorTruth tables for Boolean expressions, with tautology check and canonical forms.Probability CalculatorTwo-event probabilities (and, or, not, given) and repeated-trial odds.Chi-Square CalculatorGoodness-of-fit and independence tests with p-value and Cramér's V.T-Test CalculatorOne-sample, two-sample (Welch or pooled) and paired t-tests from raw data.Complex Number CalculatorAdd, multiply, divide and raise complex numbers, with polar form.Vector CalculatorDot and cross products, magnitude, angle and projection for 2D/3D vectors.Exponent CalculatorPowers of any base, exact big powers, and solve for the exponent or base.Number Sequence CalculatorFind the pattern, formula, next terms, nth term and sum of a sequence.Big Number CalculatorExact arithmetic, powers and factorials for integers of any size.Percentile CalculatorAny percentile of a data set, plus the percentile rank of a value (Excel methods).Box Plot MakerBox-and-whisker plots with quartiles, IQR and outliers; compare sets, download SVG/PNG.Histogram MakerTurn a list of numbers into a histogram with automatic or custom bins; download it.Weighted Average CalculatorWeighted mean of scores, grades or prices, and the score you need to hit a target.Decimal to Fraction CalculatorExact fractions for decimals and repeating decimals, plus the closest simple fraction.Rounding CalculatorRound to decimal places, significant figures or a multiple, with every rounding rule.Binary CalculatorAdd, subtract, multiply, divide and AND/OR/XOR/NOT in binary, octal, decimal or hex.IEEE-754 Float ConverterSee how a number is stored as a 32- or 64-bit float: sign, exponent, mantissa, error.Golden Ratio CalculatorSplit a length into golden sections or find the matching side, with a golden scale.Cubic Equation SolverAll three roots of ax³ + bx² + cx + d = 0, real and complex, with a graph.Karnaugh Map SolverSolve K-maps for 2–6 variables: exact minimal SOP and POS.Poisson Distribution CalculatorPoisson probabilities: exactly, at most or at least k events.Expected Value CalculatorExpected value, variance and SD of outcomes and probabilities.Factorial CalculatorExact n! to 20,000, digits, trailing zeros and gamma function.Modulo Calculatora mod n (all conventions), modular power and modular inverse.Surface Area CalculatorSurface area and volume of cylinders, cones, spheres and more.Polygon CalculatorRegular polygon area, side, apothem, radius and angles.Circle CalculatorRadius, diameter, circumference, area, arc, sector and chord.Angle ConverterDegrees, radians, gradians, DMS, turns and mils, with trig values.Summation CalculatorEvaluate sigma sums and pi products of any expression.Integral CalculatorDefinite integrals of any function, to 10+ digits, with a plot.Derivative CalculatorSymbolic first and second derivatives, slope and tangent line.Polynomial Root FinderAll real and complex roots of a polynomial up to degree 12.Pascal's Triangle GeneratorExact Pascal's triangle rows, C(n, k) lookup and Sierpiński pattern.Collatz Sequence Calculator3n + 1 sequence steps, peak value and hailstone chart.Magic Square GeneratorVerified magic squares of any order from 3 to 30.Linear Interpolation CalculatorInterpolate between two points or within a data table.Divisors CalculatorAll divisors of a number, their sum and factor pairs.Geometric Mean CalculatorGeometric, harmonic and RMS means, and average growth rate.Square Root CalculatorSquare, cube and nth roots with simplest radical form.
Everyday converters
Unit ConverterLength, weight, temperature, volume, area, speed and data size.Temperature ConverterCelsius, Fahrenheit and Kelvin, live both ways — with the landmarks chart.Height ConverterCentimetres to feet & inches and back, with the 150–210 cm chart.Weight ConverterKilograms, pounds, and stone — type in any box, read the others.Cooking ConverterCups to grams and back — with real densities for flour, sugar, butter.Shoe Size ConverterUS, UK, EU and cm shoe sizes side by side, for men's and women's fits.Ring Size ConverterUS, UK, EU sizes and millimetres — plus how to measure at home.Fuel Economy ConverterMPG (US & UK), L/100km and km/L — plus your real consumption from a trip.Recipe ScalerPaste ingredients, change servings, get quantities rescaled with real fractions.Paint CalculatorLitres or gallons and tins for a room from its size, openings and coats.Tile CalculatorTiles, boxes, grout and adhesive for a floor or wall, with waste allowance.Concrete CalculatorConcrete volume for slabs, footings, posts and steps, with bags of premix needed.BTU CalculatorAir-conditioner size for a room in BTU, tons and kW, using ENERGY STAR sizing.Wallpaper CalculatorHow many rolls of wallpaper you need, counting whole drops and pattern repeat.Flooring CalculatorBoxes of laminate, vinyl or wood for several rooms, with waste, underlay and skirting.Gravel, Mulch & Soil CalculatorVolume, tonnes and bags of gravel, mulch, topsoil or sand for any area and depth.Fence CalculatorPosts, panels, rails, pickets and post-hole concrete for a fence with gates.Roofing CalculatorRoof area from footprint and pitch, squares, shingle bundles, tiles and rafter length.Drywall CalculatorDrywall or plasterboard sheets for a room, with screws, tape and joint compound.Brick CalculatorBricks or blocks for a wall with joints, single or double skin, waste and mortar.Stair CalculatorRisers, treads, run, stringer length and angle, checked against IRC or UK rules.Board Foot CalculatorBoard feet and cost for a lumber list, plus cubic metres and cubic feet.Pool Volume CalculatorPool water in litres and gallons for any shape and slope, plus fill time and cost.Tire Size CalculatorTyre diameter, sidewall and revs per mile, and speedometer error between two sizes.Coffee Ratio CalculatorCoffee and water for pour-over, French press, AeroPress, cold brew and espresso.Pizza Dough CalculatorFlour, water, salt and yeast for any number of dough balls by baker's percentage.Aquarium CalculatorFish tank volume and true water volume, weight, substrate, heater and filter size.Sourdough CalculatorFlour, water, starter and salt for any loaf size, counting the starter's flour and water.Cake Pan ConverterScale a recipe between round, square and rectangular tins by area.Turkey Roasting CalculatorRoasting and thawing time, servings and a timeline back from dinner.Clothing Size ConverterConvert women's and men's clothing sizes between US, UK, EU, IT, AU and JP.Bra Size CalculatorBand and cup from your measurements in UK, US, EU, FR and AU sizes.Distance Between CoordinatesGreat-circle distance, bearing and midpoint between two lat/long points.Coordinate ConverterConvert lat/long between decimal, DMS, DDM, UTM and geohash.Deck CalculatorDecking boards, joists, screws and cost for a deck, in feet or metres.Plant Spacing CalculatorHow many plants for a bed, border or hedge, in grid or offset rows.Fabric Yardage CalculatorHow much fabric to buy from the pieces you'll cut, in yards or metres.ABV CalculatorHomebrew alcohol by volume from original and final gravity, with attenuation.Curtain Size CalculatorCurtain width and drop from your window, heading style and length.Grass Seed CalculatorHow much grass seed for a new lawn or overseeding, by area and grass type.Pond Liner CalculatorPond liner and underlay size, water volume and pump flow for a garden pond.Rainwater Harvesting CalculatorRainwater you can collect from a roof each year, and the tank size to fit.Rug Size CalculatorThe right rug size for a living room, dining table or bed, to standard sizes.Pool Chlorine CalculatorHow much liquid chlorine, bleach or cal-hypo to raise free chlorine.Paper Weight ConverterConvert paper gsm to US bond, text, cover and index pound weights.Horsepower CalculatorConvert hp, PS, kW and work out power from torque and rpm.CFM CalculatorAirflow in CFM for a room from air changes per hour, or a duct.Pipe Flow CalculatorPipe flow rate, velocity and Hazen–Williams head loss for water.Snow Load CalculatorWeight of snow on a roof from depth and snow type, in kPa and psf.Pressure ConverterConvert psi, bar, kPa, atm, mmHg, inHg and more, all at once.Torque ConverterConvert N·m, lb-ft, lb-in, kgf·m and more, with wrench force.Hat Size ConverterHead size in cm or inches to US, UK, EU and S/M/L hat sizes.Oven Temperature ConverterConvert gas mark, °C, fan °C and °F, with a full oven chart.Carat ConverterCarats to grams, points and grains, plus diamond size in mm.Map Scale CalculatorConvert map distances to real distances for any map scale.Model Scale ConverterConvert real sizes to model scale: HO, N, OO, 1:24, 1:72 and more.Insulation CalculatorInsulation thickness for a target R-value or RSI, and packs needed.Paver CalculatorPavers for a patio or path, plus sub-base, sand and edging.Retaining Wall CalculatorBlocks, caps, drainage gravel and base for a retaining wall.Ladder Angle CalculatorSafe ladder base distance (4-to-1 rule), reach and length.Water Heater Size CalculatorTank size from peak-hour demand, or tankless kW and BTU.Stud CalculatorWall studs at 16 or 24 inch centres, openings, plates and waste.Caulk CalculatorTubes of caulk or sealant for a joint length, width and depth.Rebar CalculatorRebar grid for a slab: bars, stock lengths, weight and ties.Attic Ventilation CalculatorAttic vent NFA with the 1/150 or 1/300 rule, intake and exhaust.Sod CalculatorTurf rolls and pallets for a lawn of rectangles and circles.Light Bulb Lumens CalculatorWatts to lumens for LED, CFL, halogen and old bulbs, and room lumens.LED Bulb Savings CalculatorMoney, energy and CO₂ saved by switching to LED, with payback.Dehumidifier Size CalculatorDehumidifier pints per day for your room size and dampness.Compost CalculatorBalance greens and browns to the ideal compost C:N ratio.Fertilizer CalculatorHow much N-P-K fertilizer to apply for a target nutrient rate.Firewood CalculatorWoodpile volume in cords, face cords and cubic metres, with heat.Tree Age CalculatorEstimate a tree's age from trunk circumference and species.Candle Making CalculatorWax and fragrance oil for a batch of container candles.Soap Lye CalculatorLye and water for cold-process soap from your oils and superfat.Brine CalculatorSalt for any brine percentage, for fermenting, pickling and meat.Yeast ConverterConvert instant, active dry and fresh yeast by grams, teaspoons or packets.Baker's Percentage CalculatorBaker's percentages, hydration and recipe scaling by flour weight.Cake Serving CalculatorServings for round, square, sheet and tiered cakes, and tiers for guests.Meat Cooking Time CalculatorRoasting times and internal temps for beef, lamb, pork and chicken.BBQ Smoking Time CalculatorSmoking times for brisket, pork butt, ribs and more, with start time.Rice to Water Ratio CalculatorWater, cooking time and yield for every kind of rice.Cocktail ABV CalculatorStrength of a mixed drink with dilution, standard drinks and units.Sugar Substitute ConverterSwap sugar for honey, maple, erythritol, allulose and more.Air Fryer ConverterConvert oven recipes to air fryer temperature and time.Slow Cooker ConverterConvert oven or stovetop times to slow cooker LOW and HIGH.
Electronics
Ohm's Law CalculatorEnter any two of volts, amps, ohms and watts — get the rest.Resistor Colour CodeRead a resistor's bands, or find the bands for a value.Solar Panel CalculatorSolar system size and panel count from your usage, with output, cost and payback.Battery Life CalculatorBattery runtime from mAh and load, duty-cycle averaging and power bank charges.Voltage Drop CalculatorVoltage drop and % for copper or aluminium cable by AWG or mm², length and load.LED Resistor CalculatorSeries resistor for LEDs, rounded to E12/E24 values, with power rating.Series & Parallel Resistor CalculatorTotal resistance in series or parallel, and the best E12/E24 pair for a target.Voltage Divider CalculatorOutput voltage from Vin, R1 and R2, or R2 for a target, with load effects.555 Timer CalculatorAstable frequency and duty cycle, monostable pulse width, and design values.RC Filter CalculatorRC low/high-pass cutoff frequency, time constant and capacitor for a target.Capacitor Code CalculatorDecode 104, 473J and 4R7 capacitor markings, and turn values into codes.SMD Resistor Code CalculatorDecode 3-digit, 4-digit, R and EIA-96 surface-mount resistor markings.Decibel CalculatorRatios to dB and back, adding sound levels, and dBm, dBu and dBV.Generator Size CalculatorRunning and starting watts of your appliances and the generator size you need.Watts to Amps CalculatorConvert watts to amps (or amps to watts) for DC, AC and three-phase.Wire Gauge ConverterConvert AWG to mm² and diameter, with copper resistance and a chart.Power Factor CalculatorkW, kVA and kVAR, plus capacitor size to correct power factor.PCB Trace Width CalculatorMinimum PCB trace width for a current (IPC-2221), with resistance.Op-Amp Gain CalculatorInverting and non-inverting op-amp gain, dB and resistor values.Zener Diode CalculatorSeries resistor and power ratings for a Zener voltage regulator.Reactance CalculatorInductive and capacitive reactance and LC resonant frequency.Transformer CalculatorTurns ratio, currents and VA rating for a transformer.Antenna Length CalculatorDipole and quarter-wave antenna lengths for any frequency.Speaker Impedance CalculatorSpeaker wiring impedance: series, parallel and series-parallel.Battery Bank CalculatorSeries/parallel battery pack voltage, Ah, Wh and runtime.
Health & everyday
BMI CalculatorBody mass index in metric or imperial, with what the number does and doesn't mean.Calorie CalculatorYour daily calories (BMR and TDEE) from the Mifflin-St Jeor equation.Macro CalculatorSplit daily calories into protein, carbs and fat by goal — in grams.Protein CalculatorDaily protein by weight and goal, with the evidence ranges stated.One Rep MaxEstimate your 1RM from any set — with the percentage training table.Body Fat CalculatorThe US Navy tape-measure method, with its accuracy stated honestly.Heart Rate ZonesYour five training zones from age — with the Karvonen method built in.Water IntakeA daily fluid estimate from weight and activity — honestly framed.Running Pace CalculatorPace, time or distance — enter two, get the third, with race splits.Sleep CalculatorThe best times to fall asleep or wake, counted in sleep cycles.Work Hours CalculatorAdd up shifts, subtract breaks, and total the week in decimal hours.Feels-Like TemperatureWind chill and heat index from the official formulas — auto-chosen.White NoiseWhite, pink and brown noise with a sleep timer — synthesised, seamless.Online RulerA real-size ruler on your screen, in centimetres or inches.Aspect Ratio CalculatorResize while keeping proportions, and find the ratio of any size.MetronomeA steady click at any tempo, with accents and tap-tempo.BPM CounterTap along to any song and read its tempo — outliers dropped.Download Time CalculatorHow long a file takes at your connection speed — Mbps vs MB/s untangled.Habit TrackerTick off daily habits and watch your streaks grow — saved on this device.Shopping ListA grocery list grouped by aisle, saved on your phone, with quantities and ticks.Meal PlannerWeekly meal plan grid that builds its own shopping list.Packing ListA trip packing list generated from trip type, days and weather — tick as you pack.Caffeine CalculatorHow much caffeine is still in you through the day and at bedtime.Pregnancy Due Date CalculatorDue date from last period, conception or IVF transfer, with week and trimester.Weekly PlannerA printable week grid: hours by days, type into cells, add priorities and notes.Chore ChartA fair rota: people and chores assigned in rotation, ticked off and printed.Workout LogLog sets, reps and weight; track personal bests, estimated 1RM and session volume.Ideal Weight CalculatorDevine, Robinson, Miller and Hamwi formulas side by side, plus the healthy BMI range.Blood Alcohol CalculatorEducational BAC estimate from drinks, weight and time using the Widmark formula.Calories Burned CalculatorCalories used by 28 activities from MET values, weight and minutes, with a day log.Steps CalculatorSteps to km or miles and back, from your stride, with walking time and calories.Fasting TimerIntermittent fasting timer for 16:8, 18:6, 20:4 and more, with history and streak.Ovulation CalculatorEstimated ovulation, fertile window and next six periods on a calendar.Waist-to-Height Ratio CalculatorWaist ÷ height with NICE health bands and the waist size to stay under.Blood Pressure CheckerClassify blood pressure readings by AHA category and average several readings.Pregnancy Weight Gain CalculatorRecommended pregnancy weight gain by BMI and week, for one baby or twins.Child Height PredictorPredict a child's adult height from the parents' heights, with the likely range.VO2 Max CalculatorEstimate VO2 max from a Cooper run, Rockport walk or resting heart rate.Daily PlannerA printable day plan: top 3, hourly schedule, to-dos, water, mood and notes.Party Food CalculatorHow much food, drinks and ice to buy for a party of any size and length.Moving Boxes CalculatorHow many boxes, tape rolls and packing paper you need for a move.Body Surface Area CalculatorBSA in m² from height and weight by Mosteller, Du Bois, Haycock and more.Alcohol Units CalculatorUK units, US standard drinks, grams and calories for the drinks you had.Conception Date CalculatorEstimate when conception happened from a due date, last period or birth date.Race Time PredictorPredict 5K, 10K, half and marathon times from one race with Riegel's formula.Lean Body Mass CalculatorLean body mass from height and weight by Boer, James and Hume, or body fat %.FFMI CalculatorFat-free mass index and the height-normalised FFMI from weight and body fat.Waist-to-Hip Ratio CalculatorWaist-to-hip ratio with WHO health-risk thresholds for men and women.Golf Handicap CalculatorWorld Handicap System index from your rounds, plus a course handicap.Bowling Score CalculatorScore a ten-pin game frame by frame with strikes, spares and the tenth.TV Viewing Distance CalculatorBest seating distance for a TV size, or the best TV size for your room.Bike Gear CalculatorGear ratios, gear inches, rollout and speed at cadence for every gear.BPM to Delay CalculatorDelay and reverb times in ms for every note value at any tempo, with tap tempo.Video File Size CalculatorFile size from bitrate and length, or the bitrate to hit a target size.Shift Schedule GeneratorRotating shift calendars: 2-2-3 Panama, 4 on 4 off, DuPont, 24/48 and custom.Recipe Card MakerPrint recipes on 4×6 or 5×7 index cards, A6, A5 or a full page.Medication Schedule MakerA printable weekly medicine chart with tick boxes for every dose.Reward Chart MakerPrintable star or sticker charts for kids: goals, days and a reward.Baby TrackerLog breastfeeds, bottles, nappies and sleep with one tap; saved on your phone.Calorie Deficit CalculatorHow long to reach a goal weight at a daily calorie deficit, with a goal date.Net Carbs CalculatorCarbs minus fibre and sugar alcohols, for US or UK/EU food labels.Sleep Debt CalculatorYour weekly sleep shortfall against your sleep need, with a recovery plan.Blood Sugar ConverterGlucose mg/dL to mmol/L and back, with fasting and after-meal ranges.A1c CalculatorHbA1c % to mmol/mol and estimated average glucose, both ways.Cholesterol Ratio CalculatorTotal/HDL ratio, non-HDL, LDL estimate and triglyceride ratio from a lipid test.Baby Formula CalculatorDaily formula amounts by weight and age, per feed, with scoops.Baby Sleep CalculatorA sample nap schedule and bedtime from your baby's age and wake time.Cycling Power CalculatorWatts needed for a speed, or speed from watts, with W/kg and drag split.Swim Pace CalculatorPace per 100 m or yd, race and triathlon swim times, and Critical Swim Speed.Workout GeneratorA random home workout for your time, focus and level, with a timer.Dew Point CalculatorDew point, absolute humidity and humidex from temperature and RH.Luggage Size CheckerCheck a bag against carry-on or checked size and weight limits.Hiking Time CalculatorHike duration from distance and ascent with Naismith's rule.Plug Type FinderPlug types, voltage and adapter needs for countries worldwide.Altitude Oxygen CalculatorEffective oxygen and air pressure at any altitude.Period TrackerPrivate cycle tracker with predictions and calendar.Mood & Gratitude JournalDaily mood, gratitude notes and patterns over time.Water Intake TrackerDaily water goal, one-tap logging and streaks.Weight TrackerLog weigh-ins and see the real trend and goal date.Blood Pressure LogHome BP diary with averages, chart and printable report.Running Plan GeneratorCouch to 5K, 10K, half and marathon training plans.
About these tools
The everyday sums: percentages and discounts, exact ages, days between dates, splitting a bill, converting units, working out loan repayments, and a countdown timer with a stopwatch.