Quick answer
Rectangle volume = length × width × depth; round = π ÷ 4 × d² × depth; oval = π ÷ 4 × L × W × depth; 1 ft³ = 7.48 gallons. A 30 × 15 ft pool with 5 ft average depth holds 2,250 ft³, or 16,831 gallons (63,713 litres).
Choose the shape and enter the dimensions and average depth. The calculator returns volume in gallons, litres and cubic feet.
Related tools: Aquarium Volume Calculator: Capacity and filled weight of a rectangular aquarium. Volume Converter: Convert litres, gallons, cups, spoons and more. Barrel Volume Calculator: Approximate capacity of a barrel from head diameter, bung diameter and length.
How to use the Pool Volume Calculator
- Choose shape: Rectangle, Round and Oval.
- Enter length (or diameter if round) (ft) (above 0).
- Optionally, enter width (rectangle and oval) (ft) (above 0).
- Enter average depth (ft) (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Shape | Choose one: Rectangle; Round; Oval | Starts at Rectangle |
| Length (or diameter if round) | A number, in ft | > 0 |
| Width (rectangle and oval) (optional) | A number, in ft | > 0 |
| Average depth | A number, in ft | > 0 |
Formula and method
Formula
rectangle: L × W × D; round: π/4 × d² × D; oval: π/4 × L × W × D; 1 ft³ = 1728 ÷ 231 US gal
IEEE-754 double precision; shown to the decimals indicated.
Use the average of the shallow and deep ends for sloped pools. Plan geometry only; confirm quantities with your supplier and local code before ordering.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Shape = Rectangle; Length (or diameter if round) = 30; Average depth = 5; Width (rectangle and oval) = 15.
| Result | Value |
|---|---|
| Pool volume | 16,831 gal |
| Liters | 63,713 |
| Cubic feet | 2,250 |
Example 2
Inputs: Shape = Round; Length (or diameter if round) = 18; Average depth = 4.5.
| Result | Value |
|---|---|
| Pool volume | 8,566 gal |
| Liters | 32,426 |
| Cubic feet | 1,145.1 |
Example 3
Inputs: Shape = Oval; Length (or diameter if round) = 24; Average depth = 5; Width (rectangle and oval) = 12.
| Result | Value |
|---|---|
| Pool volume | 8,460 gal |
| Liters | 32,026 |
| Cubic feet | 1,131 |
The first line is the headline result (pool volume). Below it the pool Volume Calculator lists liters and cubic feet, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Average depth
A pool with a 3 ft shallow end and a 7 ft deep end has an average depth of about 5 ft if it slopes evenly. Use the water depth, not the wall height.
Why volume matters
Chemical doses, heater sizing and fill time all depend on volume. At 10 gallons per minute, filling 16,831 gallons takes about 28 hours. Irregular shapes can be estimated by splitting them into simple shapes.
How the result changes with length
Holding every other input at the first worked example, this table changes only length. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Length | Pool volume | Liters | Cubic feet |
|---|---|---|---|
| 15 | 8,416 gal | 31,856 | 1,125 |
| 30 | 16,831 gal | 63,713 | 2,250 |
| 60 | 33,662 gal | 127,426 | 4,500 |
| 120 | 67,325 gal | 254,852 | 9,000 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Width (rectangle and oval): left empty shows "Enter the pool width." beside that field and no result.
- Length (or diameter if round): entering "0" shows "Length (or diameter if round) must be greater than 0." beside that field and no result.
Choosing between the Pool Volume Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Aquarium Volume Calculator](/construction/aquarium-volume/) | length, width and water height | Capacity |
| [Volume Converter](/converters/volume-converter/) | value, from and to | US gallon → Litre (L) |
| [Barrel Volume Calculator](/math/barrel-volume-capacity-calculator/) | head diameter, bung diameter and inside length | Capacity |
| [Cubic Yards Calculator](/construction/cubic-yards-calculator/) | length, width and height or depth | Volume |
| [Cylinder Cubic Footage Calculator](/construction/cylinder-cubic-footage-calculator/) | diameter, height or length and unit | Volume |
Background: construction estimates
Material quantities are geometry plus a margin. Calculate the exact volume or area, add an allowance for waste, spillage, cuts and uneven ground (calculator pages commonly mention 5 to 10 percent, a rule of thumb that varies by material and job) and round up to whole units. One cubic yard is exactly 27 cubic feet.
Suppliers often have minimum order sizes and may charge for small loads, so confirm quantities, product yields and local code with your supplier or a qualified estimator before ordering.
Assumptions and limitations
- Use the water depth, not the wall height
Quantities are estimates. Add allowances for waste and site conditions, and follow local codes and a qualified professional's instructions for structural or safety-critical work.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for width (rectangle and oval) and length (or diameter if round) to confirm this.
Frequently asked questions
How do I calculate a kidney-shaped pool?
Estimate with an oval and adjust for the shape.
How many gallons per cubic foot?
One cubic foot holds about 7.48 US gallons.
Should I use the water line?
Yes, measure to the water level.
What does the Pool Volume Calculator calculate?
Gallons of water in a rectangular, round or oval pool. It returns Pool volume, Liters and Cubic feet.
What formula does the Pool Volume Calculator use?
rectangle: L × W × D; round: π/4 × d² × D; oval: π/4 × L × W × D; 1 ft³ = 1728 ÷ 231 US gal. Use the average of the shallow and deep ends for sloped pools.
What do I need to enter in the pool Volume Calculator?
You enter Shape, Length (or diameter if round) (ft) and Average depth (ft). Optional: Width (rectangle and oval) (ft).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Use the water depth, not the wall height.
What does the “Shape” option change?
It sets how the pool Volume is worked out. The choices are Rectangle, Round and Oval.
What is an example of a pool Volume result?
With shape Rectangle, length (or diameter if round) 30, average depth 5 and width (rectangle and oval) 15, the pool volume is 16,831 gal.
Can I rely on this calculator for a decision?
Quantities are estimates. Add allowances for waste and site conditions, and follow local codes and a qualified professional's instructions for structural or safety-critical work. For this calculator in particular: Use the water depth, not the wall height.
Related calculators
- Aquarium Volume Calculator — Capacity and filled weight of a rectangular aquarium.
- Volume Converter — Convert litres, gallons, cups, spoons and more.
- Barrel Volume Calculator — Approximate capacity of a barrel from head diameter, bung diameter and length.
- Cubic Yards Calculator — Cubic yards, cubic feet and cubic meters from length, width and height.
- Cylinder Cubic Footage Calculator — Volume of a cylinder (pipe, tank, column) in cubic feet, cubic yards, gallons and liters.
- Concrete Volume Calculator — Cubic yards of concrete and bags needed for a slab, footing or pad.
Sources
- OpenStax, Prealgebra 2e (Rice University): perimeter, area, volume, circumference and the Pythagorean theorem
- NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Appendix B conversion factors (international foot 0.3048 m, inch 25.4 mm, US gallon 3.785411784 L)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.