🏊Pool Chlorine Calculator

About this tool

Enter the pool's volume, your current free chlorine (FC) reading and the target, and choose the product. The tool shows how much to add, in fluid ounces, gallons, litres, ounces, pounds or grams, and how much cyanuric acid (stabiliser) stabilised products add at the same time.

How pool chlorine dosing works

Free chlorine is measured in parts per million (ppm), which is milligrams per litre. Raising 1 ppm therefore needs 1 gram of available chlorine for every 1,000 litres, or about 37.9 g per 10,000 US gallons. The amount of product depends on its strength. Liquid chlorine (sodium hypochlorite) sold for pools is usually 10% or 12.5% available chlorine by weight per volume, and household bleach is 6% or 8.25%. Make sure it's plain, unscented bleach. A 15,000-gallon pool going from 1 to 4 ppm needs about 57.6 fl oz of 10% liquid chlorine, 46 fl oz of 12.5%, or about 96 fl oz of 6% bleach. Granular calcium hypochlorite (cal-hypo, 65–73%) adds calcium as well, and dichlor (56%) and trichlor tablets (90%) also add cyanuric acid (CYA, stabiliser): roughly 0.9 ppm and 0.6 ppm of CYA for every 1 ppm of chlorine. CYA protects chlorine from sunlight, but as it builds up it makes chlorine less effective, so the free chlorine you need rises with your CYA level. That's why many owners use liquid chlorine day to day and test CYA monthly. Honest limits: liquid chlorine and bleach lose strength in storage, especially in heat, so old product needs more. Let your test kit, not guesswork, set the target. Never mix chlorine products with each other or with acid, always add chemicals to water, and keep swimmers out until levels settle. The pool volume calculator works out your pool's volume first.

Frequently asked questions