Pool volume calculator
Every dose on a stop is a fraction of one number: how much water is in the pool. Measure the surface, average the depths, and this gives you gallons — then feed that figure into the chlorine, salt and alkalinity calculators.
Pre-filled with a common 32 × 16 ft inground pool. Change any field and the reading settles in place.
Volume
22,023gal
- Surface area
- 512 ft²
- Average depth
- 5.75 ft
- Cubic feet
- 2944 ft³
- Litres
- 83,365 L
What it measures
Volume is surface area × average depth, converted to gallons. A US liquid gallon is 231 cubic inches exactly, so a cubic foot holds 7.48 gallons. Shape only changes the surface area: a round pool is 0.785 of the square its diameter would fill, and a kidney or freeform outline is conventionally taken at 0.85 of its bounding rectangle.
Average depth is the part people get wrong. A pool that runs 3 ft 6 in at the steps and 8 ft in the deep end averages 5 ft 9 in only if the floor slopes evenly. If it has a long flat shallow shelf and a short hopper, weight the average toward the shallow end or you will over-dose every chemical you add all season.
Worked example
| Step | Working | Result |
|---|---|---|
| Surface area | 32 ft × 16 ft | 512 ft² |
| Average depth | (3.5 ft + 8 ft) ÷ 2 | 5.75 ft |
| Cubic feet | 512 × 5.75 | 2,944 ft³ |
| Gallons | 2,944 × 7.48 | 22,022 gal |
Round to the nearest 500 gallons for dosing. Nobody measures a pool to the inch, and no chemistry correction is that precise.
Measure once, write it on the lid
Volume never changes. Write it inside the equipment-pad lid or on the chemistry log and every future stop starts from a known number instead of a guess.
Dosage notes
Public pools carry turnover rules — the CDC's Model Aquatic Health Code sets maximum turnover times by pool type — so a commercial volume figure also decides the pump and filter you are allowed to run. For a residential pool the number matters most for chemistry: 1 ppm of free chlorine in 22,000 gallons takes roughly 22 fl oz of 12.5% liquid chlorine, and every ppm you miscalculate is money poured into the deep end.