💯Big Number Calculator

About this tool

Enter two whole numbers of any length; commas, spaces and underscores are ignored. Choose an operation: add, subtract, multiply, divide, mod, power, factorial, GCD or LCM. The result is shown in full with every digit, together with its digit count, the remainder for divisions and a scientific-notation approximation. Copy the result with one click.

Why big numbers need special arithmetic

Most calculators, spreadsheets and programming languages store numbers in 64-bit floating point, which holds about 15–16 significant digits. Beyond that, digits are silently lost: 2⁶⁴ appears as 1.8447E+19 rather than 18,446,744,073,709,551,616, and 30! loses its last digits. This calculator uses BigInt, the arbitrary-precision integer type built into modern browsers, so every digit is exact. 2¹⁰⁰ is 1,267,650,600,228,229,401,496,703,205,376 and 30! is 265,252,859,812,191,058,636,308,480,000,000, a 33-digit number. Exact big integers matter in cryptography, where RSA keys are hundreds of digits long, in combinatorics and in checking puzzles and proofs. Division returns the whole-number quotient and the remainder separately; the mod operation always returns a non-negative result, so −7 mod 3 is 2. The greatest common divisor uses Euclid's algorithm, and the least common multiple follows from it: lcm(12, 18) = 36. Honest limits: whole numbers only, no decimals or fractions, and very large powers and factorials are capped so the page stays responsive. The exponent calculator handles decimal powers, the prime number tool checks primality and the scientific calculator covers everyday maths.

Frequently asked questions