Pool volume calculator for home pools
How many gallons is my pool? Enter your measurements and get the volume in US gallons, imperial gallons and litres. Every chemical dose starts from this number, so the calculator shows each step of the math.
Your pool holds about
How to measure your pool
Measure the water, not the deck. Lengths and widths are taken at the water line, and depths from the water surface to the floor. In a pool with a sloping floor, take the depth at the shallow end and at the deep end. A floor that slopes evenly from one end to the other has an average depth halfway between the two.
Many backyard pools have a shallow area, a steep slope and a deep area. A single average depth can be far off for those pools. Split the pool into parts instead: each part with its own straight floor. The calculator adds the parts together, so a 20 ft flat shallow end at 3.5 ft, an 8 ft slope down to 8 ft and a 12 ft deep end, all 16 ft wide, come to 25,374 US gallons. Using one average depth of 5.75 ft for the whole 40 ft would give 27,528 gallons instead.
Kidney and irregular pools
Freehand and kidney shapes are not in this version: we have not found a published uncertainty range for estimating them, and we do not show a volume without one. If your pool can be split into rectangles and circles, work out each part with this calculator and add them up.
Gallons or litres?
US pool products are dosed per US gallon (3.785412 litres). The UK and some Canadian sources use the imperial gallon (4.54609 litres), which is about 20 % larger. Metric product labels use litres. The calculator always gives all three, so you can match the unit on your product label. One cubic foot of water is 7.48052 US gallons (NIST SP 811), and one cubic metre is 1,000 litres.
Worked examples
| Pool | US gal | Imperial gal | Litres |
|---|---|---|---|
| Rectangle 32 × 16 ft, 3.5 → 8 ft deep | 22,023 | 18,338 | 83,365 |
| Round above-ground 24 ft, 4 ft deep | 13,536 | 11,271 | 51,241 |
| Oval (ellipse) 20 × 12 ft, 4.5 ft deep | 6,345 | 5,283 | 24,019 |
| Rectangle 10 × 5 m, 1.5 m deep | 19,813 | 16,498 | 75,000 |
All numbers on this page are calculated by the same code as the calculator. The formulas and the published test cases are on the methodology page.
Disclaimer: GoodToSwim.com gives estimates for home (residential) chlorine pools based on published primary sources. It does not cover spas, hot tubs or bromine, and it does not report water quality at beaches, lakes, rivers or other open water. It never tells you that your water is safe to swim in. Results depend on your test accuracy, your pool volume and the real strength of your product. They do not replace the product label, local health regulations or a qualified pool professional. Public and commercial pools must follow local code.