How to use it
Pick shape and units
Choose rectangle, round or oval, then switch between feet and metres to match your tape measure.
Enter dimensions and depths
Type the surface dimensions plus the shallow and deep-end depths. For a constant-depth pool, enter the same depth twice.
Read the volume
Gallons, litres and cubic metres update live as you type — no button to press.
Why pool volume matters
Almost every pool maintenance decision starts with volume. Chemical dosing — chlorine, shock, pH adjusters, algaecide — is specified per 10,000 gallons or per cubic metre, so an inaccurate volume means over- or under-dosing every time. Pump and filter sizing also depends on volume: a pump is typically chosen so it can turn over the entire pool in about 8 hours, and heaters are rated by how many gallons they can raise per hour.
Worked example: a 16 × 32 ft rectangular pool with a 3 ft shallow end and an 8 ft deep end has an average depth of (3 + 8) ÷ 2 = 5.5 ft. Volume = 16 × 32 × 5.5 × 7.48 ≈ 21,065 US gallons. The formulas used here are: rectangle L × W × average depth × 7.48; round π × (diameter ÷ 2)² × average depth × 7.48; oval L × W × average depth × 0.89 × 7.48 — the 0.89 factor accounts for the rounded ends. In metres, the calculator computes cubic metres first, then litres (m³ × 1,000) and US gallons (litres ÷ 3.785).
Questions
US gallons or UK gallons?
US gallons. Pool chemical labels and pump ratings in North America use US gallons (1 US gallon ≈ 3.785 litres). If you need UK imperial gallons, divide the litres figure by 4.546.
How accurate is the oval factor?
The 0.89 factor is the standard industry approximation for oval pools with fully rounded ends. For a true ellipse the exact factor is π ÷ 4 ≈ 0.785, and for an oval with straight sides and semicircular ends it lands between the two, so 0.89 is a practical middle estimate. For chemical dosing, being within a few percent is fine.
What if my pool has one depth?
Enter the same depth in both the shallow-end and deep-end fields. The average of two equal values is that value, so the calculation is exact for constant-depth pools.
Is anything uploaded?
No. The whole calculation runs in your browser — nothing is uploaded, and the tool is free with no sign-up.