Pool Volume Calculator
Enter your pool size and depths to find how much water it holds.
What this tool does
A rectangular pool's volume is length × width × average depth. A pool 20 ft × 10 ft with depths from 3 ft to 6 ft has an average depth of 4.5 ft, so 900 cubic feet, or about 6,732 US gallons (25,485 litres). Choose your shape and enter the size above.
Multiplies the surface area by the average depth.
Converts the cubic volume into gallons and litres.
How to use it
- Choose the pool shape and units.
- Enter the length (or diameter) and width.
- Enter the shallow and deep depths.
- Read the volume in the unit you need.
Why use this calculator
Works out the volume of a rectangular, round or oval pool from its size and its shallow and deep depths, in US gallons, imperial gallons, litres and cubic metres. Pool chemicals, heaters, pumps and covers are all sized to the volume of water. Guessing is expensive, because too much chemical wastes money and too little leaves the water unsafe.
Why we built it
We built the pool volume calculator for rectangular, round and oval pools with shallow and deep depths. Convert units with the litres to gallons converter and compare with the volume calculator.
Who this tool is for
- Pool owners dosing chemicals
- Buyers comparing pool sizes
- Installers estimating water volume
When to use it
- Dosing chemicals for a pool or hot tub.
- Sizing a pump, heater or cover.
- Estimating the cost to fill or heat it.
- Buying a new pool.
How it works
Volume = surface area × average depth. A rectangle uses length × width, a round pool π × (diameter ÷ 2)² and an oval pool π ÷ 4 × length × width. The average depth is (shallow + deep) ÷ 2, which is exact for a steady slope. One cubic foot holds 7.48052 US gallons; one cubic metre holds 1,000 litres or 264.172 US gallons.
Example: 8 m × 4 m with depths 1 m to 2 m is 48 m³, which is 48,000 litres or about 12,680 US gallons.
A pool with a flat shallow end and a sloping deep end holds more or less than the simple average. Measure each part separately for an accurate figure.
A worked example
These are the values the calculator opens with, so you can see exactly what it does with them. Change any value on the page and the result updates; the figures below come from the same calculation.
| Input | Value |
|---|---|
| Pool shape | Rectangle |
| Units | Feet |
| Length | 20 |
| Width | 10 |
| Depth at the shallow end | 3 |
| Depth at the deep end | 6 |
With those inputs, the calculator returns:
- Pool volume: 6,732 US gallons
- Litres: 25,485
- Cubic metres: 25.49
- Imperial gallons: 5,606
- Average depth: 4.5 ft
- Surface area: 200 ft²
What you give it, and what you get back
| Item | Details |
|---|---|
| Shape and units | Rectangle, round or oval; feet or metres. |
| Size | Length (or diameter) and width. |
| Depths | Shallow-end and deep-end depths. |
| Output | US and imperial gallons, litres, cubic metres, average depth and area. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| Chemical dosing feels off | The pool shape is irregular. | Measure sections separately. |
| Gallons: US or UK | They differ by 20%. | Both are shown. |
| Above-ground pools | They are filled to a level below the wall. | Use the actual water depth. |
Assumptions and limitations
- Regular shapes with a steady slope.
- Does not account for steps or benches.
Frequently asked questions
How do I calculate the volume of a pool?
Multiply the surface area by the average depth.
How many gallons is a 20×10 pool?
With an average depth of 4.5 ft, about 6,732 US gallons.
What is the average depth?
The shallow depth plus the deep depth, divided by two.
How do I convert cubic feet to gallons?
Multiply by 7.48052.
Can I use it for a hot tub?
Yes. Enter the dimensions and the water depth.
Is my information sent anywhere?
No. The calculation runs in your browser and nothing leaves the page.