Above ground pool gallons by size and wall height
Wall height is not water depth. Pool makers size the water line below the top rail, and the capacity charts use 3.5 ft of water in a 48 in wall, 4 ft in a 52 in wall and 4.5 ft in a 54 in wall. The table below uses the same depths.
| Pool | 48 in wall | 52 in wall | 54 in wall |
|---|---|---|---|
| 12 ft round | 2,970 | 3,400 | 3,820 |
| 15 ft round | 4,650 | 5,310 | 5,970 |
| 18 ft round | 6,690 | 7,650 | 8,600 |
| 21 ft round | 9,110 | 10,410 | 11,710 |
| 24 ft round | 11,890 | 13,590 | 15,290 |
| 27 ft round | 15,050 | 17,200 | 19,350 |
| 30 ft round | 18,590 | 21,240 | 23,890 |
| 33 ft round | 22,490 | 25,700 | 28,910 |
| 12 × 24 ft oval | 5,950 | 6,800 | 7,650 |
| 15 × 30 ft oval | 9,290 | 10,620 | 11,950 |
| 16 × 32 ft oval | 10,570 | 12,080 | 13,590 |
| 18 × 33 ft oval | 12,270 | 14,020 | 15,770 |
| 18 × 38 ft oval | 14,120 | 16,140 | 18,160 |
| 21 × 41 ft oval | 17,780 | 20,320 | 22,860 |
The formulas
Round: diameter × diameter × water depth × 5.9 = gallons
Oval: length × width × water depth × 5.9 = gallons
Lengths in feet, depth in feet of water. A 24 ft round pool with a 54 in wall holds 24 × 24 × 4.5 × 5.9 = 15,290 gallons; an 18 × 33 ft oval with a 52 in wall holds 18 × 33 × 4 × 5.9 = 14,020 gallons. The 5.9 is π ÷ 4 × 7.48 gallons per cubic foot.
If your pool is not full to the line
Type your real water depth instead of the preset: switch the depth box to the measured value in the calculator above. An inch lower than the chart is about 2 % fewer gallons. If the floor is deeper in the middle (a hopper or a slope), measure the average of the shallow and deep spots.
Once you know the gallons, the pool chlorine calculator and the salt calculator use them. For inground sizes and other shapes see the pool gallon calculator; a plain round pool is on the round pool volume calculator.
Water depths per wall height: pool-trade capacity charts (48 in = 3.5 ft, 52 in = 4 ft, 54 in = 4.5 ft). Factor 5.9 = π ÷ 4 × 7.48. Read October 18, 2026.
Frequently asked questions
How many litres does a 21 ft round above ground pool hold?
With a 48 in wall (3.5 ft of water) about 9,110 gallons, which is 34,470 litres. With a 52 in wall 10,410 gallons or 39,400 litres, and with a 54 in wall 11,710 gallons or 44,320 litres.
What is the best shape for an above ground pool?
Round is the cheapest and strongest, and it holds the most water per foot of wall. Oval suits a narrow yard but needs support posts. The gallons formula is the same π/4 factor for both, so the shape does not change how you dose or heat.
How do you calculate above ground pool water volume?
Round: diameter × diameter × water depth × 5.9. Oval: length × width × water depth × 5.9. Use the water depth, not the wall height: the trade charts assume 3.5 ft of water in a 48 in wall, 4 ft in 52 in and 4.5 ft in 54 in.
How many gallons does a 15x30 above ground pool hold?
It is an oval, so 15 × 30 × depth × 5.9: 9,290 gallons with a 48 in wall, 10,620 with a 52 in wall and 11,950 with a 54 in wall. Fill to the skimmer line and these are the gallons for every dose.
How much water is in an 18 ft round above ground pool?
About 6,690 gallons in a 48 in wall, 7,650 in a 52 in wall and 8,600 in a 54 in wall. That is 18 × 18 × water depth × 5.9. A pool filled an inch lower holds about 2 % less.