All calculators
Pick a topic. Each calculator works in US units or metric, and shows how it got the answer.
Pool size and water
Volume is the number every dose depends on. Start here, then work out fill time, normal water loss and partial drains.
All 4 pool size and water calculatorsWater chemistry
Exact doses for chlorine, shock, salt, pH, alkalinity, stabilizer and calcium, plus a water-balance check.
All 9 pool chemistry calculators- Pool Chemical CalculatorAll your test results in, one dosing plan out
- Pool Chlorine CalculatorLiquid, bleach, tablets or powder to raise FC
- Pool Shock CalculatorShock dose for algae, cloudy water or chloramines
- Pool Salt CalculatorPounds and bags of salt to reach your target
- Pool pH CalculatorAcid or soda ash to move pH to target
- Pool Alkalinity CalculatorBaking soda to raise TA, acid to lower it
- Pool Stabilizer (CYA) CalculatorCyanuric acid to add, or how much to drain
- Pool Calcium Hardness CalculatorCalcium chloride to add, or how much to drain
- LSI Calculator (Saturation Index)Is your water corrosive, balanced or scaling?
Equipment and energy
Size pumps, filters, heaters and salt cells, and see what heating and pumping really cost.
All 6 pool equipment and energy calculators- Pool Pump Size CalculatorFlow rate (GPM) from volume and turnover
- Pool Filter Size CalculatorMinimum filter area for your flow rate
- Pool Heater Size CalculatorBTU output needed, using the DOE method
- Salt Chlorine Generator Size CalculatorWhich salt cell rating your pool needs
- Pool Heating Cost CalculatorHeat-up and monthly cost by heater type
- Pool Pump Running Cost CalculatorElectricity cost, and variable-speed savings
Hot tubs
Volume, chemical doses and monthly running cost for acrylic, inflatable and wooden tubs.
All 3 hot tub calculatorsTarget levels at a glance
Where each reading should sit in a typical outdoor home pool. The full chemistry chart explains each one and lists the sources.
| Reading | Aim for | Why it matters | Fix it with |
|---|---|---|---|
| Free chlorine | Depends on CYA, e.g. 5–7 ppm at 40 CYA | Kills germs and algae. Stabilizer slows it down, so the target rises with CYA. | chlorine |
| pH | 7.4–7.6 | Comfort, chlorine strength and scale. The CDC range is 7.0–7.8. | ph |
| Total alkalinity | 80–120 ppm | Buffers pH so it doesn’t swing. | alkalinity |
| Calcium hardness | 200–400 ppm plaster | Too low etches plaster, too high leaves scale. | calcium hardness |
| Stabilizer (CYA) | 30–50 ppm | Shields chlorine from sunlight. Public pools are capped at 90 ppm. | stabilizer (cya) |
| Salt (salt pools) | Your cell’s range, often ~3,200 ppm | The cell turns it into chlorine. | salt |
Every answer shows its working
Open “Show the working” under any result to see the formula with your numbers in it. Below each calculator you’ll find the method, a worked example you can check by hand, and links to the sources: the CDC’s Model Aquatic Health Code, the U.S. Department of Energy, ENERGY STAR, the EPA and published water chemistry.
Start with your pool’s volume
Every chemical dose scales with the amount of water. Work out your pool’s volume once with the pool volume calculator and this site remembers it on your device, then offers it in every other calculator. Hot tub owners can do the same with the hot tub volume calculator.