Pool Volume Calculator
Gallons in a rectangular or round pool from its dimensions.
Input sheet
DIY at your own risk. Calcora's calculators and guides are general estimates and information only — not professional, engineering, legal, or safety advice. Always verify local building codes and permit requirements, and hire a licensed pro for electrical, gas, plumbing, structural, or any work you're not fully comfortable doing yourself.
Every pool chemical dose on the bottle is written per 10,000 gallons, so an accurate volume is the difference between balanced water and a green pool. This calculator handles the two common shapes — rectangular and round — using average depth.
How it works
Rectangular: length × width × average depth. Round: π × radius² × depth. Multiply cubic feet by 7.48 to get gallons.
The math is the tank formula plus one adjustment: because most pools slope from a shallow to a deep end, you use the average depth — (shallow + deep) ÷ 2 — in place of a single depth. A 3 ft to 7 ft pool computes as 5 ft.
Cubic feet convert to gallons at 7.48 per cubic foot. Round pools use π × radius² × depth, with the 'length' field carrying the diameter.
Rectangular: length × width × average depth × 7.48. Round: π × (diameter ÷ 2)² × average depth × 7.48.
Worked examples
A 32 × 16 ft in-ground pool sloping 3 ft to 7 ft. → About 19,149 gallons.
Average depth = 5 ft; 32 × 16 × 5 = 2,560 cu ft × 7.48 ≈ 19,149 gallons.
A 24 ft round above-ground pool with 4 ft of water. → About 13,500 gallons.
π × 12² × 4 ≈ 1,810 cu ft × 7.48 ≈ 13,535 gallons.
Tips & gotchas
- Measure water depth, not wall height — an above-ground pool with 52 in walls typically holds about 48 in of water.
- Keep the gallon figure with the pool supplies; every shock, chlorine, and algaecide dose starts from it.
- Kidney and freeform pools: approximate as a rectangle at about 85% of the bounding length × width, or ask the builder for the as-built volume.
FAQ
Why does volume matter?
Every chemical dose — chlorine, shock, algaecide — is rated per 10,000 gallons. Wrong volume means wrong dosing.
Why 7.48 gallons per cubic foot?
A US gallon is 231 cubic inches and a cubic foot is 1,728 — 1,728 ÷ 231 = 7.48. It is a fixed conversion, not an estimate.
Does volume change how big a pump I need?
Yes — pumps and filters are sized to turn the full volume over about once every 8 hours. A 19,000 gallon pool wants roughly 40 gallons per minute of real flow.
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