How Many Gallons in a Pool?
A quick calculator plus a reference chart of gallons for the most common pool sizes.
Pool Volume
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Common pool sizes and their approximate gallons
The table below uses the same formulas as our full Pool Volume Calculator -- length × width × average depth × 7.5 for rectangular pools, and diameter squared × average depth × 5.9 for round pools -- applied to the most commonly searched residential pool sizes, assuming a typical average depth for each.
| Pool size | Shape | Assumed avg depth | Approx. gallons |
|---|---|---|---|
| 12 × 24 ft | Rectangular | 4.5 ft | 9,720 gal |
| 14 × 28 ft | Rectangular | 5 ft | 14,700 gal |
| 16 × 32 ft | Rectangular | 4.5 ft | 17,280 gal |
| 18 × 36 ft | Rectangular | 5 ft | 24,300 gal |
| 20 × 40 ft | Rectangular | 4.5 ft | 27,000 gal |
| 15 ft round | Round | 4 ft | 5,310 gal |
| 18 ft round | Round | 4 ft | 7,646 gal |
| 24 ft round | Round | 4 ft | 13,594 gal |
| 27 ft round | Round | 4.5 ft | 19,349 gal |
These are starting points, not a substitute for measuring your own pool -- actual average depth is the biggest source of difference between your real pool and the chart. Use the calculator above with your own numbers whenever you can.
Where these numbers come from
The formulas and default values in this calculator are based on:
- same standard pool-volume formulas used industry-wide (7.5 multiplier for rectangular pools, 5.9 for round/oval pools)
- typical average depths assumed for each listed size based on common residential and above-ground pool specifications
These are planning estimates. Test your actual water, follow product labels, and check your equipment manufacturer's guidance before you buy or dose chemicals.
Frequently asked questions
Is there one single 'gallons per size' number I can just look up?
Not reliably -- two pools of the same length and width can hold very different amounts of water if their average depth differs, which is common even within the same nominal size. The chart above assumes a typical depth for each size, but your own pool's volume calculator result will always be more accurate.
How much does depth change the gallon count?
A lot. Adding just 1 foot of average depth to a 16 x 32 ft pool adds about 3,840 gallons -- more than 20% of its total volume at 4.5 ft average depth. Always double check your average depth before relying on a volume figure for chemical dosing.
Do I need to know my exact gallons to add chemicals?
You need a reasonably close number -- within about 10% is fine for routine maintenance. Use this page or the full Pool Volume Calculator with your pool's real dimensions rather than the size-chart estimate whenever you're about to dose chemicals.
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