Answer first
What this calculator tells you
Calculate a pool's volume in gallons, cubic feet and liters from its size and average depth. Get the volume right before you dose chemicals, size a pump or order a fill. Formula: Gallons = length × width × average depth × 7.48052 (rectangle) or × 5.87486 (round or oval, which is π ÷ 4 of that). At the worked-example inputs, the water volume (US gallons) is 19,150.1. Holding every other input steady, moving length or diameter (ft) from 26 to 38 moves the result from 15,559.5 to 22,740.8.
Transparent method
The formula
Get the volume right before you dose chemicals, size a pump or order a fill.
Worked example
Example inputs
How to interpret the result
Every chemical dose and pump rating depends on how many gallons the pool holds, and guessing by eye is off by thousands. A 32 by 16 foot rectangle averaging five feet deep holds about 19,150 gallons. A round or oval pool of the same outer size holds about 78.5 percent as much, because the corners are missing.
At the worked-example inputs the water volume (US gallons) is 19,150.1. It rises with width (ft), average depth (ft) and length or diameter (ft) and falls as pool shape increases.
These are material-quantity estimates. Always add a waste and overage margin, and confirm actual coverage with your specific product and supplier before purchasing.
Before you rely on it
What to check
Average the depth properly. Add the shallow and deep ends and halve, and for a sloped floor use a measurement partway along.
The common error
Where people go wrong with pool volume calculator
Using the deepest depth as the average. That overstates the volume, and the chemicals you dose from it come out too strong.
Sensitivity evidence
How length or diameter (ft) changes the water volume (US gallons)
Holding every other input at the worked-example value, moving length or diameter (ft) from 26 to 38 moves the water volume (US gallons) from 15,559.5 to 22,740.8: a spread of 7,181.3, or 38% of the worked-example result.
| Length or diameter (ft) | Water volume (US gallons) | Volume (cubic feet) | Volume (liters) |
|---|---|---|---|
| 26 | 15,559.5 | 2,080 | 58,899 |
| 29 | 17,354.8 | 2,320 | 65,695.1 |
| 32worked example | 19,150.1 | 2,560 | 72,491.1 |
| 35 | 20,945.5 | 2,800 | 79,287.2 |
| 38 | 22,740.8 | 3,040 | 86,083.2 |
Every input, tested
Which input moves the water volume (US gallons) most
Of the 4 inputs, width (ft) moves the water volume (US gallons) most (4,787.5 across the range tested) and length or diameter (ft) moves it least (3,590.6).
| Input | Tested from | To | Water volume (US gallons) at each end | Swing |
|---|---|---|---|---|
| Width (ft) | 14 | 18 | 16,756.4 to 21,543.9 | 4,787.5 (25%) |
| Pool shape | Rectangle or square | Round or oval | 19,150.1 to 15,039.6 | 4,110.5 (21%) |
| Average depth (ft) | 4.5 | 5.5 | 17,235.1 to 21,065.1 | 3,830 (20%) |
| Length or diameter (ft) | 29 | 35 | 17,354.8 to 20,945.5 | 3,590.6 (19%) |
Two variables at once
Water volume (US gallons) by length or diameter (ft) and width (ft)
Across the grid the water volume (US gallons) runs from 12,642.1 to 27,004.7. Moving length or diameter (ft) from 26 to 38 shifts it by 7,181.3 at the middle column, and moving width (ft) from 13 to 19 shifts it by 7,181.3 at the middle row, so neither is the bigger lever here.
| Length or diameter (ft) \ Width (ft) | 13 | 16 | 19 |
|---|---|---|---|
| 26 | 12,642.1 | 15,559.5 | 18,476.9 |
| 29 | 14,100.8 | 17,354.8 | 20,608.8 |
| 32 | 15,559.5 | 19,150.1 | 22,740.8 |
| 35 | 17,018.2 | 20,945.5 | 24,872.7 |
| 38 | 18,476.9 | 22,740.8 | 27,004.7 |
The highlighted cell is the worked example: 19,150.1.
Step by step
The worked example, input by input
| Input | Value used | What it means |
|---|---|---|
| Length or diameter (ft) | 32 | Enter the length or diameter (ft) used in this calculation. |
| Width (ft) | 16 | For a round pool, enter the same number as the diameter. |
| Average depth (ft) | 5 | Add the shallow and deep ends and divide by two. |
| Pool shape | Rectangle or square | Sets the gallons-per-cubic-foot factor. |
| Water volume (US gallons) | 19,150.1 | |
| Volume (cubic feet) | 2,560 | |
| Volume (liters) | 72,491.1 | |
Inputs, definitions and assumptions
Length or diameter (ft)
Enter the length or diameter (ft) used in this calculation. The prefilled worked-example value is 32.
Width (ft)
For a round pool, enter the same number as the diameter. The prefilled worked-example value is 16.
Average depth (ft)
Add the shallow and deep ends and divide by two. The prefilled worked-example value is 5.
Pool shape
Sets the gallons-per-cubic-foot factor. The prefilled worked-example value is Rectangle or square.
How to use this calculator
- 1Verify the inputs. Gather length or diameter (ft), width (ft), average depth (ft) and pool shape from your own documents; the prefilled values are examples.
- 2Save a baseline. The worked example puts the water volume (US gallons) at 19,150.1. Store your own version of it as Scenario A.
- 3Test one change. Start with width (ft), the input with the biggest effect here: moving width (ft) from 14 to 18 takes the water volume (US gallons) from 16,756.4 to 21,543.9, a swing of 25% of the worked-example figure.
- 4Check the extremes. At half the example width (ft) (8) the water volume (US gallons) is 9,575.1; at double (32) it is 38,300.3.
People also ask
Frequently asked questions
How do you calculate pool volume?
Gallons = length × width × average depth × 7.48052 (rectangle) or × 5.87486 (round or oval, which is π ÷ 4 of that). At the worked-example inputs the water volume (US gallons) is 19,150.1.
What does the pool volume result mean?
Get the volume right before you dose chemicals, size a pump or order a fill. At the worked-example inputs the water volume (US gallons) is 19,150.1. It rises with width (ft), average depth (ft) and length or diameter (ft) and falls as pool shape increases.
How much does length or diameter (ft) change the water volume (US gallons)?
Holding every other input at the worked-example value, moving length or diameter (ft) from 26 to 38 moves the water volume (US gallons) from 15,559.5 to 22,740.8, a spread of 7,181.3.
What are the limits of this pool volume calculator?
These are material-quantity estimates. Always add a waste and overage margin, and confirm actual coverage with your specific product and supplier before purchasing. The tables on this page test length or diameter (ft) only from 26 to 38; a value outside that range is not tabulated here.
Which input moves the water volume (US gallons) most in the pool volume calculator?
Ranked by how far each moves the water volume (US gallons) across the range tested: width (ft) (4,787.5, 25%), pool shape (4,110.5, 21%), average depth (ft) (3,830, 20%) and length or diameter (ft) (3,590.6, 19%).
If I double width (ft) in the pool volume calculator, does the water volume (US gallons) double?
Doubling it from 16 to 32 takes the water volume (US gallons) from 19,150.1 to 38,300.3, which is 2.00 times the worked-example figure. So the result scales almost exactly in proportion. Halving it to 8 gives 9,575.1.
How much does width (ft) matter in the pool volume calculator?
The worked example uses 16. Holding every other input at its worked-example value, moving width (ft) from 14 to 18 takes the water volume (US gallons) from 16,756.4 to 21,543.9, a swing of 25% of the worked-example figure.
How much does average depth (ft) matter in the pool volume calculator?
The worked example uses 5. With the other inputs left at the worked example, moving average depth (ft) from 4.5 to 5.5 takes the water volume (US gallons) from 17,235.1 to 21,065.1, a swing of 20% of the worked-example figure.
How much does pool shape matter in the pool volume calculator?
The worked example uses Rectangle or square. With the other inputs left at the worked example, switching pool shape changes the water volume (US gallons): rectangle or square gives 19,150.1; round or oval gives 15,039.6.
Which inputs change the volume (cubic feet) in the pool volume calculator?
At the worked-example inputs it is 2,560. Length or diameter (ft) takes it from 2,320 to 2,800, width (ft) takes it from 2,240 to 2,880, average depth (ft) takes it from 2,304 to 2,816 and pool shape takes it from 2,560 to 2,010.5.
Which inputs change the volume (liters) in the pool volume calculator?
At the worked-example inputs it is 72,491.1. Length or diameter (ft) takes it from 65,695.1 to 79,287.2, width (ft) takes it from 63,429.7 to 81,552.5, average depth (ft) takes it from 65,242 to 79,740.2 and pool shape takes it from 72,491.1 to 56,931.2.
Why does hardwood need a bigger pilot hole than softwood for the same screw?
Hardwood is denser and less able to compress or flex around a screw's threads without splitting. A slightly larger pilot hole relieves some of that stress before the screw is driven, at the cost of very slightly less thread grip than the same screw would get in softwood.
Sources and evidence
Free Calculators Online is independent and is not affiliated with or endorsed by the source organizations. Educational estimates only.