Pool Volume Calculator — gallons and litres
Gallons from the pool's shape and its shallow and deep ends, with the exact 231 in³ gallon, in gallons, litres and cubic metres.
How many gallons a pool holds, from its shape and the shallow and deep ends, with the exact gallon — the number every chemical dose and every fill-up starts from.
| Surface area | — |
|---|---|
| Average depth | — |
| Volume | — |
| US gallons | — |
| Litres | — |
Average depth is the whole trick. A pool with a shallow end and a deep end and a straight slope between them holds surface area times the average of the two depths. A 30 × 15 pool from 3½ to 8 feet averages 5¾ feet: 2,587 cubic feet, about 19,400 gallons. A pool with a flat shallow shelf and a sudden drop holds more than the average says, and one with a hopper bottom holds less; for those, measure the depth at several points and average them, then enter that as both ends.
Gallons are 231 cubic inches, exactly. That makes 7.480519 US gallons to the cubic foot, and the page uses that figure rather than 7.5. On 20,000 gallons the rounded factor is off by 50 gallons, which is a few ounces of chlorine either way — small, but there is no reason to be wrong.
Oval is an ellipse, and kidney pools are not. The oval here is π/4 × length × width, which is right for a true oval. A kidney or freeform pool is closer to 0.45 × length × width, which is a rule of thumb the page does not offer as a button; enter the oval and take about ten percent off, or measure the surface as pieces.
Rectangle = L × W; round = π (d ÷ 2)²; oval = π/4 × L × W. Volume = area × (shallow + deep) ÷ 2. 1 US gallon = 231 in³ (exact), so 1 ft³ = 7.480519 gal = 28.316846592 L.
Worked example
A 30 × 15 ft pool, 3½ ft at the shallow end and 8 ft at the deep end: how many gallons?
- Surface 450 ft²; average depth (3.5 + 8) ÷ 2 = 5.75 ft.
- 450 × 5.75 = 2,587.5 ft³.
- × 7.480519 = 19,356 US gallons (73.3 m³, 73,270 L).
About 19,400 gallons. A 24 ft round pool 4½ ft deep is 2,036 ft³, 15,228 gallons. The gallon is 231 in³ exactly; 7.5 per cubic foot is close and wrong by 50 gallons here.
9 values on this page were driven in a browser and compared with independently derived figures on 2026-09-05 (474 values across 56 calculators site-wide).
Questions
How do you calculate pool gallons?
Surface area × average depth × 7.480519. A 30 × 15 ft pool from 3½ to 8 ft holds 2,587 ft³, about 19,400 gallons.
How many gallons in a cubic foot?
7.480519, because a US gallon is exactly 231 cubic inches (1,728 ÷ 231).