Chlorine Dosing Calculator
Enter your pool volume, current and target free-chlorine readings, and the product you’re using, to estimate how much to add. Guidance only — always confirm against your product’s label and re-test afterward.
Chlorine to add
How the dose is calculated
Free-chlorine ppm is a concentration — milligrams of active chlorine per liter of water — so raising it by a fixed amount takes more chlorine in a bigger pool. The calculator converts your pool volume to liters, multiplies by the ppm increase you want to a get a target mass of active chlorine, then divides by your product’s percentage of available chlorine to find how much of the actual product (which is diluted or blended with other ingredients) you need to add.
Liquid products are reported in fluid ounces (and gallons for larger doses); granular products like cal-hypo and dichlor are reported by weight in ounces and pounds, since that’s how they’re measured and sold.
Frequently Asked Questions
What free chlorine level should I be targeting?
Most residential pools without stabilizer are kept around 1-3 ppm free chlorine for everyday swimming, with many guidelines recommending a minimum of roughly 1 ppm. A shock treatment — used to clear cloudy water, a strong chlorine smell, or after heavy bather load or a storm — commonly targets a much higher level, often around 10 ppm free chlorine, then is left to fall back into the normal range before swimming resumes. Always check the specific guidance for your pool type and local health authority.
Why does the chlorine product I use matter?
Different chlorine products carry a different percentage of 'available chlorine' by weight — a 12.5% liquid chlorine solution delivers more active chlorine per fluid ounce than a 10% solution, and granular cal-hypo or dichlor carry their own strengths again. This calculator scales the dose to the product's stated percentage, so double-check the % on your specific jug or bag before dosing, since it can vary by manufacturer and even by batch.
Why is my calculated dose different from what my pool store recommends?
This tool uses a standard chemistry-based formula (parts per million as milligrams of active chlorine per liter of water) and a simplifying density assumption for liquid products. Real-world doses can shift slightly with water temperature, sunlight (chlorine breaks down faster in strong UV without stabilizer), and how thoroughly the chemical is mixed in. Treat the result as a solid starting point and re-test with a kit afterward rather than a guaranteed exact figure.
Is it safe to combine chlorine products?
Never mix chlorine products directly with each other or with acids — some combinations can react violently or release dangerous gas. Add one product at a time, always to water (not water to concentrated product), and follow the safety instructions and storage guidance printed on the label.
Dosing guidance only, not a substitute for the manufacturer's instructions or a professional water test. Pool chemicals can be hazardous — read and follow the product label, add chemicals to water (never water to chemical), never mix different products together, and keep them out of reach of children and pets.