How to use the pool volume calculator
- Pick the shape: rectangle, round, oval, oval with straight sides, kidney or half circle.
- Measure the inside of the pool in feet and inches, or choose Meters. For a round pool, measure straight across the middle. To add up several lengths first, use the feet and inches calculator.
- Measure the water, not the wall. Depth is from the water line to the floor. If the floor slopes, choose Shallow and deep end and type both.
- For an L-shaped or free-form pool, press Add a section and measure it as pieces. The sections are added together.
The result shows US gallons, liters, Imperial gallons, cubic feet and cubic meters. Open Time to fill and type your hose's flow to see roughly how long filling will take.
Pool volume formula
Volume is the surface area of the water times its average depth. The calculator works out each shape's area in square feet, multiplies by the depth to get cubic feet, then converts:
| Shape | Surface area |
|---|---|
| Rectangle | length x width |
| Round | 3.1416 x diameter x diameter / 4 |
| Oval | 3.1416 x length x width / 4 |
| Oval with straight sides | (length - width) x width + 3.1416 x width x width / 4 |
| Kidney | (A + B) x length x 0.45 |
| Half circle | 3.1416 x diameter x diameter / 8 |
With a sloping floor, the average depth is (shallow + deep) / 2. That assumes the floor slopes evenly from end to end. If the deep end is a short, steep hopper, measure the shallow part and the deep part as two sections.
Gallons per cubic foot. NIST's tables give 4 quarts = 1 gallon (gal) = 231 cubic inches
and 1,728 cubic inches in a cubic foot, so one cubic foot holds 1,728 / 231 = 7.4805 US gallons. Pool guides often round this to 7.5, and use 5.9 for round and oval pools, which is 7.48 x 3.1416 / 4 rounded. The calculator uses the exact figures, so its answers can differ slightly from a rounded rule.
How many gallons in my pool?
Here is a 32 x 16 ft in-ground pool, 3 ft 6 in deep at the shallow end and 8 ft at the deep end. Press Try an example to see it in the calculator.
| Step | Working | Result |
|---|---|---|
| Surface area | 32 x 16 | 512 sq ft |
| Average depth | (3.5 + 8) / 2 | 5.75 ft |
| Volume | 512 x 5.75 | 2,944 cu ft |
| US gallons | 2,944 x 7.4805 | 22,023 |
| Liters | 2,944 x 28.317 | 83,365 |
Steps, benches and rounded corners take a little water out, so a real pool of this size usually holds a bit less. To work out the soil dug out for a new pool, use the cubic yard calculator.
Above ground pool gallons
Round above ground pools are sold by diameter and wall height, but the water sits a few inches below the top of the wall. Measure your actual water depth. This table is worked out with the round formula above:
| Diameter | 48 in of water | 52 in of water | 54 in of water |
|---|---|---|---|
| 12 ft | 3,384 gal | 3,666 gal | 3,807 gal |
| 15 ft | 5,288 gal | 5,728 gal | 5,949 gal |
| 18 ft | 7,614 gal | 8,249 gal | 8,566 gal |
| 21 ft | 10,364 gal | 11,227 gal | 11,659 gal |
| 24 ft | 13,536 gal | 14,664 gal | 15,228 gal |
For example, a 24 ft pool with 52 in of water: 3.1416 x 24 x 24 / 4 = 452.4 sq ft, x 4.333 ft = 1,960 cu ft, x 7.4805 = 14,664 gallons.
Pool volume calculator for oval pools
"Oval" means two different shapes, and they hold quite different amounts. A true oval (an ellipse) curves all the way round. Most above ground oval pools have two straight sides and round ends. For a 15 x 30 ft pool with 4 ft of water:
| Shape | Area | Gallons |
|---|---|---|
| Oval (ellipse) | 3.1416 x 30 x 15 / 4 = 353.4 sq ft | 10,575 |
| Oval with straight sides | 15 x 15 + 3.1416 x 15 x 15 / 4 = 401.7 sq ft | 12,020 |
The straight-sided pool holds about 14% more. If your pool has straight sides, pick that shape so the count is not too low. The surface areas here are also what you need for a cover; the square footage calculator handles other shapes.
Pool volume calculator for kidney pools
Kidney pools have no single exact formula, because every curve is different. The calculator uses a rule of thumb from pool suppliers: area = (A + B) x length x 0.45, where A and B are the widths across the two widest points and length is the longest distance end to end. One pool supply guide describes it as adding the distance across from the two widest points (A + B)
, then multiplying by the length and 0.45.
A kidney pool 30 ft long, 10 ft and 15 ft across its two ends, with an average depth of 5 ft: (10 + 15) x 30 x 0.45 = 337.5 sq ft, x 5 = 1,687.5 cu ft, or about 12,623 gallons.
For a closer figure, measure the pool as pieces instead: for example, a round section for each end and a rectangle between them, each added with Add a section. A half circle shape is there for rounded ends.
Pool volume calculator in litres
In meters the sums are simpler: length x width x average depth gives cubic metres, and each cubic metre is 1,000 litres. A pool 8 x 4 m, 1.2 m deep at one end and 2 m at the other, averages 1.6 m: 8 x 4 x 1.6 = 51.2 m³, or 51,200 litres.
That is about 13,526 US gallons, or 11,262 Imperial gallons. The UK gallon is larger than the US one: the Weights and Measures Act 1985 defines it as 4.54609 cubic decimetres
, that is 4.54609 litres, against 3.785 litres for the US gallon.
How long will it take to fill my pool?
Time to fill = volume / flow rate. Garden hoses vary a lot with water pressure, so measure yours: time how long it takes to fill a bucket of known size. A 5 gallon bucket that fills in 30 seconds is 10 gallons a minute. At that rate, the 22,023 gallon example pool takes 2,202 minutes, about 36 hours 42 minutes.
Check with your water supplier before filling a large pool, and do not leave a hose running unwatched.
Pool volume and chemicals
Knowing your pool's volume is the first step to dosing chemicals, but this calculator does not work out doses. Products differ in strength, so follow the directions on the product label for the gallons or liters you have.
In Excel or Google Sheets
With the length in A2, the width in B2 and the average depth in C2, all in feet, the US gallons in a rectangular pool are:
=A2*B2*C2*1728/231
For a round pool with the diameter in A2 and the depth in C2:
=PI()*(A2/2)^2*C2*1728/231
Microsoft's help page says PI Returns the number 3.14159265358979, the mathematical constant pi
, and Google's says it returns the value of pi to 9 decimal places
. Multiply cubic feet by 28.316846592 for liters.
Questions and answers
How many gallons are in a cubic foot of water?
About 7.48 US gallons. A US gallon is 231 cubic inches and a cubic foot is 1,728 cubic inches, so 1,728 / 231 = 7.4805.
How do I find the average depth of my pool?
Add the depth at the shallow end and the deep end and divide by 2. A pool 3.5 ft at one end and 8 ft at the other averages 5.75 ft. Measure to the water line, not the top of the wall.
How many gallons are in a 24 ft round above ground pool?
With 52 inches of water, about 14,664 US gallons. With 48 inches, about 13,536 gallons. Measure your own water depth, as it is usually a few inches below the wall.
How accurate is the kidney pool formula?
It is an approximation, because kidney curves differ. For a closer figure, split the pool into round and rectangular sections and add them up.
How many liters are in a US gallon?
3.785411784 liters exactly. An Imperial (UK) gallon is 4.54609 liters.
Can I use this to work out how much chlorine to add?
It gives you the volume, which product labels ask for, but it does not work out doses. Follow the directions on the product you use.
Sources
Checked on 13 October 2026. If a rule has changed, please tell us.
- NIST Handbook 44 (2026), Appendix C: General Tables of Units of Measurement (gallon, cubic foot, liter)
- Weights and Measures Act 1985, Schedule 1 (gallon: 4.54609 cubic decimetres)
- Pinch A Penny: How do you calculate your pool's volume? (kidney pool rule)
- Microsoft Support: PI function
- Google Docs Editors Help: PI