Pool and hot tub calculators
Pick the job you're doing. Most chemistry tools need your pool's volume first. Work it out once and the other tools remember it in this browser.
Pool size
Gallons and surface area: the numbers every other tool needs.
Pool chemistry
How much chlorine, acid, stabilizer or salt to add, and why.
- Chlorine calculatorSee how much chlorine to add to reach the right free chlorine level for your pool's stabilizer, in ounces, gallons or pounds of the product you actually have.
- Pool shock calculatorWork out the shock level your pool actually needs and how much product gets you there. For algae it depends on your stabilizer; for a "chlorine smell" it depends on combined chlorine.
- pH calculatorFind how much acid lowers your pH, or how much soda ash raises it. The dose comes from a water-chemistry model that accounts for your alkalinity.
- Alkalinity calculatorRaise alkalinity with the right amount of baking soda, or lower it safely with acid and aeration. The total acid and a safe first-round dose are worked out for you.
- CYA (stabilizer) calculatorGet the stabilizer amount to raise CYA, or the share of water to replace to lower it, plus the free chlorine level your new CYA calls for.
- Salt calculatorFind how much salt to add, in pounds and bags, to reach the level your salt chlorine generator needs.
Equipment & energy
Pump run time, running costs and heater sizing.
- Pump run time calculatorWork out how many hours your pump needs each day to filter all your water, from your pool size and flow rate.
- Pump energy cost calculatorSee what your pump costs to run each month and season, and what a variable-speed pump at lower speed could save.
- Heat pump sizing calculatorEstimate the heater output (BTU/h) your pool needs from its surface area and climate, using the Department of Energy's sizing rule, plus how long and how much it costs to heat up.
Opening & closing
Seasonal checklists with the chemical amounts filled in.
Hot tubs & spas
Small-water chemistry and what a hot tub costs to run.
- Hot tub volume calculatorGet the maximum your hot tub could hold from its inside measurements, and how to find its true capacity for dosing.
- Hot tub chemical calculatorEnter your hot tub's size and test results; get each chemical to add, in the right order, in grams and ounces.
- Hot tub electricity costEstimate what your hot tub adds to your electric bill each month, using its tested standby power and your local temperatures.