Pool, hot tub & pond calculators
Pool math has one input that matters more than any other: gallons. Chlorine, acid, salt and heater size are all calculated from your volume, so a wrong volume quietly spoils every dose after it.
Start by getting volume right, then use the chemical and heating calculators. They cover pools, hot tubs and ponds, and the chemical tools show before and after gauges so you can see what a dose does.
Use this first
Pool volume calculatorEvery chemical and heating result uses your volume. It handles rectangle, round, oval, oblong and kidney pools, with a flat or sloped floor.Find your volume
- Pool volume calculatorUse it when you need the gallons in a pool of almost any shape.
- Hot tub volume calculatorUse it when you do not know what your spa holds.
- Pond liner size & volume calculatorUse it when you are planning a pond or buying a liner.
Balance and sanitize
- Pool chemical calculatorUse it when you have test results and want doses for chlorine, pH, alkalinity, calcium and stabilizer, in order.
- Pool shock calculatorUse it when you want a shock or SLAM dose for your stabilizer (CYA) level.
- Pool salt calculatorUse it when you run a saltwater pool and need pounds of salt to reach your cell’s target.
- Hot tub chemical calculatorUse it when you are balancing a spa, where the ranges differ from a pool.
Heat it
- Pool heater size & heat-up cost calculatorUse it when you are sizing a heater or want to know what a heat-up will cost.
Pool chemicals are hazardous. Read the product label, never mix chemicals, and add chemicals to water, not water to chemicals. Where published sources disagree (for example on free chlorine targets), the page says which one the calculator follows.
Every calculator lists the sources it was checked against, and how we test explains the process. Your inputs stay in your browser.