Pick your pool shape, enter the dimensions, and get gallons — the one number every chemical dose depends on. Worth writing down.
The pool volume formula
gallons = length × width × average depth × shape factor
rectangular: 7.5 · round: 5.9 · oval: 6.7
The shape factor converts cubic feet to gallons (1 cu ft = 7.48 gal) while correcting for the shape's area. Round pools use diameter for both length and width; ovals use the long and short axes.
A worked example
A 32 × 16 ft inground pool sloping from 3 ft to 7 ft: average depth is (3 + 7) ÷ 2 = 5 ft, so volume is 32 × 16 × 5 × 7.5 = 19,200 gallons. Round it to 19,000 and write it on the inside of your equipment-pad door — every dose calculation for the life of the pool uses it.
When to distrust the estimate
Freeform pools, tanning ledges, and swim-outs all displace water the formula can't see. If your chemical doses consistently overshoot or undershoot the predicted change, correct your working volume: add a known amount of chlorine, measure the actual FC rise, and scale — our chlorine calculator makes that comparison easy.
Frequently asked questions
How do I calculate how many gallons my pool is?
Multiply length × width × average depth (all in feet), then multiply by a shape factor: 7.5 for rectangular pools, 5.9 for round pools, and 6.7 for ovals. A 32×16 ft rectangular pool averaging 5 ft deep holds 32 × 16 × 5 × 7.5 = 19,200 gallons.
How do I find my pool's average depth?
For a pool with a constant slope, add the shallow-end depth and the deep-end depth and divide by 2. A 3 ft shallow end and 8 ft deep end averages 5.5 ft. For pools with a drop-off, estimate section by section.
Why does pool volume matter so much?
Every chemical dose — chlorine, salt, acid, stabilizer — is calculated per gallon. If your volume estimate is 20% off, every dose you ever add is 20% off in the same direction, which is how pools drift into chronic problems.
How many gallons is a 24-foot round pool?
A 24 ft round above-ground pool with 4 ft of water holds about 24 × 24 × 4 × 5.9 = 13,594 gallons.