How to Calculate Pool Volume in Gallons (Standard Formulas)
Calculating your swimming pool's water volume requires determining the surface area, multiplying by the average water depth, and converting the resulting cubic volume to liquid US gallons (1 cubic foot = 7.48052 gallons).
Gallons = Length × Width × Avg Depth × 7.48
Standard box pool geometry.
Gallons = Diameter² × Depth × 5.9
Or: π × Radius² × Depth × 7.48.
Gallons = Length × Width × Avg Depth × 5.9
Accounts for curved semi-circle ends.
Common Pool Sizes & Gallon Capacity Chart
Compare your swimming pool against typical residential above-ground and inground pool sizes:
| Pool Type | Dimensions | Average Depth | Approx. Gallons | Approx. Liters |
|---|---|---|---|---|
| Round Above-Ground | 18 ft Diameter | 4 ft | 7,600 gal | 28,770 L |
| Round Above-Ground | 24 ft Diameter | 4.5 ft | 15,300 gal | 57,910 L |
| Small Inground | 12 × 24 ft | 4.5 ft (3 to 6 ft) | 9,700 gal | 36,700 L |
| Standard Inground | 16 × 32 ft | 5.5 ft (3 to 8 ft) | 21,060 gal | 79,720 L |
| Large Inground | 20 × 40 ft | 5.5 ft (3 to 8 ft) | 32,900 gal | 124,540 L |
Frequently Asked Questions (FAQ)
How do I calculate pool volume with a shallow end and deep end?▼
Add the shallow depth to the deep-end depth and divide by 2 to get average depth. For example, depths of 3 ft and 8 ft produce an average depth of 5.5 ft.
Why is knowing exact pool volume important for chemicals?▼
Pool chemicals are dosed by water volume. An inaccurate estimate can lead to under-treatment, poor water quality, over-treatment, swimmer discomfort, or equipment and liner damage.
How many gallons is a 12 × 24 ft pool?▼
A 12 × 24 ft rectangular pool with an average depth of 4.5 ft holds approximately 9,696 US gallons. At a constant depth of 4 ft, it holds approximately 8,617 gallons.
How do I size a pool pump based on gallon capacity?▼
For an eight-hour turnover, divide total pool gallons by 480 minutes to estimate the minimum gallons-per-minute flow rate. Account for plumbing resistance and manufacturer guidance when selecting equipment.