Fill level decides the number, not wall height — and the difference between a 42-inch pool and a 52-inch pool is more than 1,300 gallons, enough to change your chemical doses, filter runtime, and refill bill. The charts below cover the common sizes, then explain why published tables disagree by a few hundred gallons.
15 Ft Pool Gallon Chart By Size And Water Depth
Match your pool’s shape and actual waterline to the row below — that is the number to use for dosing and pump sizing.
| Pool Size | Water Depth | Approx. Gallons |
|---|---|---|
| 15 ft round | 42 in | 4,646 |
| 15 ft round | 48 in | 5,288–5,310 |
| 15 ft round | 52 in | 5,700–5,974 |
| 15 x 30 oval above-ground | 48 in wall | 9,293 |
| 15 x 30 oval above-ground | 52 in wall | 10,620 |
| 15 x 30 rectangle, 4 ft avg depth | 4 ft average | ~11,782 |
| 15 x 30 rectangle, 5 ft avg depth | 5 ft average | ~16,900 |
Notice how far apart “15 ft pool” answers land once the shape changes: a round 15-footer at 4,646 gallons and a 15 x 30 rectangle at 16,900 gallons are both described as 15 ft pools in casual conversation. If you are shopping rather than filling, our tested roundup of 15 ft pool picks for small yards covers which shapes and wall heights actually fit a typical backyard.
How The Gallon Charts Are Calculated
Round pools use one multiplier and rectangular pools use another, which is why the same “15” number produces very different totals depending on shape.
- Round pools: diameter × diameter × average depth × 5.9 = US gallons.
- Rectangular pools: length × width × average depth × 7.48 (or 7.5) = US gallons.
- Oval pools: charts typically carry precomputed oval multipliers rather than the round formula, so 15 x 30 oval figures do not come from either equation above.
Why Published Charts Disagree
Most of the spread comes down to two variables: how high the water actually sits, and how each source rounds its math.
Charts also differ on whether they assume a full wall or a realistic waterline, and some round 5,288 up to 5,310 while others round differently at the same depth. In-ground 15 x 30 numbers should never be swapped for above-ground oval numbers, because average-depth assumptions for a hopper-bottom pool and a flat-bottom oval are not the same thing.
FAQs
Does a 15 ft round pool really hold 5,000 gallons?
Only at the deeper fill levels. A 15 ft round pool holds about 4,646 gallons at 42 inches of water, roughly 5,310 gallons at 48 inches, and up to 5,974 gallons at 52 inches. Most owners land between 5,000 and 5,400 gallons once the water sits below the skimmer opening.
Why do two charts give me different numbers for the same pool?
Charts assume different waterline heights and round their results differently. A manufacturer chart may calculate at the full wall height while a retailer chart assumes a realistic fill line a few inches lower.
Can I use a 15 x 30 above-ground oval number for an in-ground pool?
No. In-ground 15 x 30 pools are usually rectangular with a sloped bottom, so average depth runs deeper than a flat-bottom oval. Published in-ground estimates range from about 11,782 gallons at 4 ft average depth up to roughly 16,900 gallons at 5 ft.
References & Sources
- Robelle. “Pool Water Capacity Chart.” Source of the round and oval pool gallon figures used in the chart above.
- Energy Kinetics. “Pool Size by Gallons.” Supports the round-pool multiplier and depth-based capacity ranges.