Estimate the water in a rectangular, oval, or circular pool from its internal dimensions. Results include US gallons and litres, an optional known spa volume, and a browser-only My Pool profile you can reuse in the pump calculator.
Deterministic estimate
Calculate pool volume
Choose the closest simple shape and enter internal water dimensions. The result is an estimate for planning—not a substitute for measured fill data or equipment instructions.
Hydropolis · My Pool
Estimated water volume
- Shape
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- Pool only
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- Spa
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- Filtered system volume
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- Formula
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- Method
- pool-volume-v1
A geometric estimate can differ from actual fill volume because of steps, benches, curves, water level, and construction tolerances.
Method
| Shape | Geometric volume |
|---|---|
| Rectangular | length × width × average depth |
| Circular | π × (diameter ÷ 2)² × average depth |
| Oval | π ÷ 4 × length × width × average depth |
When shallow and deep measurements are supplied, the calculator uses their arithmetic mean. Cubic feet are converted using 28.316846592 litres per cubic foot, and litres are converted using 3.785411784 litres per US gallon. Metric dimensions produce cubic metres before conversion to litres.
Worked example
A rectangular pool measuring 30 ft × 15 ft with a 5 ft average depth has a geometric volume of 2,250 cubic feet: about 16,831 US gallons or 63,713 litres. Steps, benches, curves, sloped transitions, and the actual waterline can make the filled volume different.
Assumptions and limitations
- Measure the water space, not the outside of the pool shell.
- The simple shapes do not subtract steps, benches, islands, or large curves.
- An average of shallow and deep depth is a practical approximation, not a survey of an irregular floor.
- The result does not prescribe chemical treatment or prove hydraulic performance.
- Use measured fill data, construction records, or equipment instructions when they provide a more exact volume.
Next, estimate a pump operating scenario, review what to check when a pump will not prime, or open My Pool.
Sources
- NIST Guide to the SI, Appendix B: conversion factors (exact international-foot basis; accessed 29 July 2026).
- NIST Special Publication 1020: conversion factors for general use (exact US-gallon basis; accessed 29 July 2026).