Pool Volume Calculator

How to Calculate Pool Volume

Measure your pool's dimensions (length, width, diameter, or end widths depending on shape).
Measure the actual water depth — not the pool-wall height.
Calculate the surface area for your pool's shape.
Multiply the surface area by the average water depth to get cubic feet.
Convert cubic feet to your preferred unit — US gallons, litres, or cubic metres.

Pool Volume Formulas by Shape

Rectangle: surface area = length × width; volume = surface area × average depth.
Round: area = π × (diameter ÷ 2)²; volume = area × average depth.
Oval: area = π × (length ÷ 2) × (width ÷ 2); volume = area × average depth.
Kidney (approximation): area ≈ 0.45 × (width A + width B) × length; volume = area × average depth.
Irregular/freeform: no single formula — break the pool into supported sections and add their volumes together.

How to Measure Your Pool

Measure the actual water depth, not the pool-wall height — the wall is often taller than the water line, so using wall height will overestimate the volume. Measure dimensions at the waterline where practical, since that's what actually determines the water's footprint.

How to Calculate a Pool With a Shallow and Deep End

Use the average of the shallow and deep end depths — (shallow depth + deep depth) ÷ 2 — as the depth in the volume formula. This is an estimate: it assumes a reasonably even slope between the two ends, which won't exactly match every pool floor.

How to Calculate an Irregular or Freeform Pool

There is no single formula for a truly irregular shape. Instead, break the pool into sections that match the supported shapes above (for example, a rectangle plus a round end), calculate each section's volume independently, and add them together using "+ Add pool section."

Pool Volume Conversion

1 US gallon = 231 cubic inches exactly, so 1 cubic foot = 1728 ÷ 231 ≈ 7.4805 US gallons. 1 cubic foot ≈ 28.32 litres, and 1 cubic foot ≈ 0.0283 cubic metres. The calculator uses these exact relationships internally rather than a rounded 7.5 gallons-per-cubic-foot approximation.

Pool Volume Examples

A 30 ft × 15 ft rectangular pool with a constant 5 ft depth is 2,250 cubic feet — about 16,831 US gallons. The same pool with a 3 ft shallow end and 8 ft deep end averages to 5.5 ft deep, giving about 18,514 US gallons.

Frequently Asked Questions

How many gallons are in my pool?

It depends on your pool's shape, dimensions, and actual water depth. Enter those into the calculator above to get an estimated volume in US gallons, litres, cubic feet, and cubic metres.

How do I calculate pool gallons?

Calculate the surface area for your pool's shape, multiply by the average water depth to get cubic feet, then multiply by 7.48 (more precisely, 1728 ÷ 231) to convert cubic feet to US gallons.

How do I calculate a pool with a shallow and deep end?

Use the average of the shallow and deep depths — (shallow + deep) ÷ 2 — as the depth in the volume formula. This is an estimate, since the floor's actual slope affects the true volume.

How do I calculate an irregular pool?

Break the pool into multiple sections using the supported shapes (rectangle, round, oval, kidney), calculate each section's volume independently, then add them together. Use "+ Add pool section" above to do this.

Should I measure pool-wall height or water depth?

Measure the actual water depth, not the pool-wall height. The wall is often taller than the water line, so using wall height will overestimate the actual water volume.

How many litres are in a US gallon?

One US gallon is approximately 3.785 litres. The calculator converts internally using exact cubic-foot-based conversions, not rounded approximations.