Pool volume calculator
This pool volume calculator finds how much water a rectangular, round or oval swimming pool can hold. Enter dimensions in metres or feet and get the result in litres, cubic metres and gallons.
For a sloping floor, enter the shallow-end and deep-end depths. The calculator uses their arithmetic mean, which is more useful than treating the whole pool as if it had the maximum depth.
Water volume
48,000 L
48 m³ · 1,695.1 ft³
Average depth
1.5 m
12,680 US gallons · 10,559 Imperial gallons
Formula
V = length × width × average depth
Current-value substitution
8 × 4 × 1.5 ≈ 48 m³
This is the geometric volume. The actual fill to the operating waterline is usually lower.
Pool volume formulas
- Rectangular pool: V = length × width × average depth.
- Round pool: V = π × (diameter ÷ 2)² × average depth.
- Oval pool: V = π ÷ 4 × length × width × average depth.
- Average depth = (shallow depth + deep depth) ÷ 2.
- One cubic metre equals exactly 1,000 litres.
Pool water volume example
A rectangular pool is 8 m long and 4 m wide, with depths from 1.2 to 1.8 m. Its average depth is (1.2 + 1.8) ÷ 2 = 1.5 m. The geometric volume is 8 × 4 × 1.5 = 48 m³, or 48,000 litres.
That figure assumes the entered depth reaches the waterline. If the normal waterline sits below the rim, the actual fill will be lower.
Litres, cubic feet and gallons
| Unit | Exact relationship |
|---|---|
| 1 m³ | 1,000 L |
| 1 ft³ | 28.316846592 L |
| 1 US gallon | 3.785411784 L |
| 1 Imperial gallon | 4.54609 L |
Why the actual fill may differ
- Water stops below the top edge, so measure depth to the operating waterline.
- Steps, tanning ledges, benches and rounded corners reduce the usable volume.
- Above-ground pool walls can bow slightly, making any simple geometric result an estimate.
- Use actual water volume and the equipment manual when checking filtration turnover.
- Follow the label of a specific pool chemical for dosing; volume alone does not determine safe use.
Frequently asked questions
How do I calculate pool volume in litres?
Calculate the pool volume in cubic metres from its shape, then multiply by 1,000. For example, 12.5 m³ is 12,500 litres.
How do I calculate a round pool's volume?
Multiply π by the square of half the diameter and by average depth: V = π × (d ÷ 2)² × h.
Which depth should I use for a sloping pool?
For an even slope, add the shallow and deep depths and divide by two to get the average depth.
Are US and Imperial gallons the same?
No. A US gallon is 3.785411784 litres, while an Imperial gallon is 4.54609 litres. The calculator reports both separately.
Does the calculator account for steps and benches?
No. The base formula treats the pool as a solid geometric shape, so large steps and ledges reduce actual volume.
Updated: 2026-08-16