How to use the pool volume calculator
- Pick your pool shape. For above-ground ovals with straight sides, choose “Oval above-ground”.
- Enter the size in feet or metres (inches and centimetres work too).
- Choose same depth (most above-ground pools) or shallow & deep end for in-ground pools.
- Enter the water depth, not the wall height.
Pool volume formulas
Rectangle: Length × Width × Average depth × 7.48 Round: π × Radius² × Depth × 7.48 (radius = diameter ÷ 2) Oval: π ÷ 4 × Length × Width × Depth × 7.48 Kidney: 0.45 × (A + B) × Length × Depth × 7.48 Average depth = (Shallow + Deep) ÷ 2 Litres = US gallons × 3.785 · m³ = litres ÷ 1,000
All measurements in feet give gallons. In metric, multiply metres to get cubic metres, then × 1,000 for litres.
Worked example
A 32 × 16 ft in-ground pool, 3.5 ft shallow end and 8.5 ft deep end:
- Average depth = (3.5 + 8.5) ÷ 2 = 6 ft
- Volume = 32 × 16 × 6 = 3,072 ft³
- Gallons = 3,072 × 7.48 = 22,980 US gallons (about 87,000 litres)
Common above-ground pool volumes (52 in wall, 48 in water)
| Pool size | US gallons | Litres |
|---|---|---|
| 12 ft round | 3,384 | 12,810 |
| 15 ft round | 5,288 | 20,016 |
| 18 ft round | 7,614 | 28,823 |
| 21 ft round | 10,364 | 39,231 |
| 24 ft round | 13,536 | 51,241 |
| 27 ft round | 17,132 | 64,852 |
| 15 × 30 ft oval (straight sides) | 12,020 | 45,500 |
Using your pool volume
Once you know the volume, you can work out almost everything else. Chemical doses scale directly with volume — use our Pool Chemical Calculator. Pump turnover is volume ÷ pump flow: a 20,000 gallon pool with a 50 gallon-per-minute pump turns over in 400 minutes, about 6.7 hours. Heater sizing and running cost depend on volume and surface area, and filling time is volume ÷ your hose flow rate — a garden hose delivering 9 gallons per minute fills 15,000 gallons in about 28 hours. Write your pool volume on the pump room wall or in your phone so you always have it when you test.
Tips for an accurate volume
- Measure inside the walls, not the outside of the frame or coping.
- Freeform pools: split them into rectangles and circles, calculate each, and add them up.
- Hopper-bottom pools (a deep area in the middle) hold less than the simple average suggests — estimate the deep section separately.
- Check your water meter the next time you fill or top up the pool for a real-world figure.
- Add the spa separately if it shares water with the pool.
- Re-check after a big refill or a liner change — a new liner can sit a few inches lower or higher.