Formulas
- Rectangle: length × width × average depth × 7.48 gal/ft³
- Round: π × (diameter/2)² × average depth × 7.48 (≈ 5.9 × diameter² × depth)
- Oval: π/4 × length × width × depth × 7.48
- Kidney: 0.45 × (A + B) × length × depth × 7.48, a standard approximation
Average depth is (shallow + deep) ÷ 2, which is right for a constant slope. For pools with a long flat shallow area and a short hopper, split the pool into sections and add them up. Hot tubs: use the manufacturer’s fill volume; seats and foot wells make measurements unreliable.
The most accurate method is a water meter: note the reading before and after a fill.
FAQ
How many gallons is a 16 x 32 pool?
With a 3.5 ft shallow end and a 6 ft deep end (average 4.75 ft), about 18,200 gallons.
How many gallons per cubic foot?
7.48 US gallons. One cubic meter is 264.2 US gallons (1,000 liters).