How to measure your pool
- Pick the shape. Rectangle (including most in-ground pools with square corners), round (most above-ground pools), oval, or kidney.
- Measure the inside of the pool at the water line, in feet.
- Measure the water depth at the shallow end and the deep end. For a flat-bottom above-ground pool, enter the same depth twice.
Pool volume formulas
Each shape gives a surface area. Multiply it by the average depth to get cubic feet, then by 7.48 to get gallons:
Round: diameter² × 0.785 × average depth × 7.48 (about diameter² × depth × 5.9)
Oval: length × width × 0.785 × average depth × 7.48
Kidney: (narrow width + wide width) × length × 0.45 × average depth × 7.48
Average depth = (shallow end + deep end) ÷ 2
One US gallon is 3.785 liters. The kidney formula is the standard pool trade approximation; free-form pools vary, so treat the result as close rather than exact.
How many gallons in common pool sizes
| Pool | Average depth | Gallons |
|---|---|---|
| Round 18 ft above-ground | 4 ft | 7,614 |
| Round 24 ft above-ground | 4.5 ft | 15,228 |
| Oval 15 × 30 ft | 4.5 ft | 11,897 |
| Kidney 30 ft long, 10 and 14 ft wide | 4.5 ft | 10,907 |
| Rectangle 16 × 32 ft | 4.5 ft | 17,235 |
Worked example
A 16 × 32 ft rectangular pool that is 3.5 ft at the shallow end and 5.5 ft at the deep end has an average depth of 4.5 ft. 16 × 32 × 4.5 = 2,304 cubic feet, and 2,304 × 7.48 = about 17,235 gallons (65,242 liters).
What to do with the number
- Salt water pools: find how much salt to add with the pool salt calculator.
- Chlorine: dose liquid chlorine, bleach or granules with the pool chlorine calculator.
- Filling the pool: your water bill shows the cost per 1,000 gallons, so you can price a fill or a top-up.
- Heating: heater and pump sizing both start from the pool volume. See running costs with the electricity cost calculator.
Frequently asked questions
How do I calculate how many gallons are in my pool?
Multiply the surface area by the average depth to get cubic feet, then multiply by 7.48. For a rectangle that is length × width × average depth × 7.48.
How many gallons is a 24 ft round pool?
About 15,200 gallons at an average depth of 4.5 ft, or about 13,500 gallons at 4 ft (24 × 24 × 0.785 × depth × 7.48).
How many gallons is a 16 × 32 pool?
About 17,200 gallons with a 3.5 ft shallow end and a 5.5 ft deep end (average depth 4.5 ft).
How do I find the average depth of a pool?
Add the shallow end depth and the deep end depth and divide by 2. A pool that is 3.5 ft and 5.5 ft deep has an average depth of 4.5 ft.
How many liters are in a gallon?
One US gallon is 3.785 liters, so a 15,000 gallon pool holds about 56,800 liters.
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Last updated October 2026.