Are pool capacity and pool water volume the same?
Here both mean water currently held at the entered depth. A manufacturer's maximum or advertised capacity may use a different fill level.
Pool Volume Calculator
How many gallons is your pool? Estimate water capacity from its inside dimensions and water depth, then carry the volume into fill-time or salt planning.
Published by Pool Cost Planner. Updated October 19, 2026.
Use water dimensions, not the outside dimensions of the pool.
Measure the water, not the pool wall
Use the length and width at the waterline. For a round pool, measure the diameter across its center, not the circumference. Depth runs from the water surface to the floor, not from the top rail. A 48-inch wall does not mean 48 inches of water. Manufacturer capacity at a stated fill level can be more useful than an outside-size calculation.
Constant, average and sloping water depth
Choose constant depth for a flat floor. Use a known average depth only when it represents the whole water footprint. The shallow/deep option assumes a uniform slope over a symmetric footprint; it is not reliable for a deep diving well, large shelf, steps or a sudden drop. Break irregular pools into measured sections and add their volumes without overlapping them. This calculator does not model a freeform outline or a straight-sided oval with semicircular ends.
Pool volume formulas
All dimensions must use the same length unit. Multiplying horizontal water area by average water depth gives volume. An ellipse has continuously curved sides; treating a stadium-shaped pool as an ellipse can underestimate capacity.
| Shape | Water area | Water volume |
|---|---|---|
| Rectangle | Length x width | Length x width x average depth |
| Circle | pi x diameter squared / 4 | pi x diameter squared x average depth / 4 |
| Ellipse | pi x length x width / 4 | pi x length x width x average depth / 4 |
How many gallons are in a 24 ft round pool?
At an actual, constant water depth of 4 ft, a 24 ft diameter round pool holds about 13,536 US gallons. A different water depth changes that answer directly. These are geometric examples, not specifications for a particular pool model.
| Measured water dimensions | Model | Estimated capacity |
|---|---|---|
| 20 x 10 ft; 3 to 7 ft water depth | Rectangle, uniform slope | 7,480.52 US gal / 28,316.85 L |
| 24 ft diameter; 4 ft water depth | Circle, constant depth | About 13,536 US gal |
| 10 m diameter; 1.2 m water depth | Circle | 94.24778 m3 |
| 10 x 4 m; 1.5 m water depth | Ellipse | 47.12389 m3 |
Methodology and measurement limits
The calculator stores dimensions in meters and converts cubic meters to liters and US gallons. One international foot is exactly 0.3048 m; one US gallon is 3.785411784 L. Display rounding does not change the stored volume. Surface area here means the horizontal water footprint, not the walls, floor finish or liner purchase area. A small depth error applies across the entire footprint, so measured results are estimates even when the arithmetic is exact.
Sources and review scope
Sources checked October 19, 2026. Model-specific instructions are not universal guidance. No independent professional review is claimed.
- NIST: international foot and SI conversions. Updated February 3, 2026.
Related calculators and guides
- Plan a fill from remaining volume and measured flow: Pool Fill Time Calculator.
- Use volume with a measured salinity and equipment-specified target: Pool Salt Calculator.
- Choose a supported water-planning tool: Pool Chemical Calculator.
- Build an ongoing ownership budget: Pool Cost Calculator.
FAQ
Does this pool gallon calculator use US gallons?
Yes. The gallon output is US liquid gallons, not Imperial gallons. Liters and cubic meters are also shown.
Can I estimate a kidney-shaped pool?
Not accurately with these three shapes. Obtain a documented capacity or add nonoverlapping measured subvolumes. Do not treat the longest length and widest width as a rectangle without accounting for the missing area.
Can I use this area to buy a liner?
No. Liner dimensions and interior finish area require wall depths, slopes, steps and manufacturer-specific measurements.