Pool volume calculator
Choose the shape, enter the size and the depth at both ends, and see the gallons your pool holds. Add the flow of your hose to see how long it takes to fill.
This answer is for the example values in the boxes above. a rectangular pool 24 by 12 ft, 3.5 to 5.5 ft deep, 10 gallons a minute. Change the boxes to see your own answer.
The water is the area of the surface times the average depth. A cubic foot holds 1,728 / 231 gallons, which is 7.4805.
How it works
The calculator takes the area of the water’s surface, multiplies it by the average depth, and changes the cubic feet to gallons. For a rectangle the area is the length times the width. A round pool is a circle across its length. An oval is an ellipse, which is pi over 4 times the length times the width, so a kidney or other freeform outline is only roughly covered.
Measure the water and not the wall. The two depths are averaged, and the answer is exact when the floor slopes evenly from the shallow end to the deep end. Leave the deep end empty for a floor of one depth.
A worked example
A pool 24 feet long and 12 feet wide has a surface of 288 square feet. The floor is 3.5 feet deep at one end and 5.5 at the other, so the average depth is 4.5 feet. That makes 1,296 cubic feet, which is 9,695 gallons, 36,699 liters or 36.7 cubic meters.
A round pool 15 feet across and 4 feet deep holds 5,288 gallons. An oval of 24 by 12 feet and 4.5 feet deep holds 7,614. A flat pool of 10 by 15 feet and 3 feet deep holds 3,366.
Filling it
Type the flow of your hose in gallons a minute to see how long the pool takes to fill. At 10 gallons a minute the first pool takes 16 hours 9 minutes. The calculator divides the gallons by the flow, so it assumes that the flow stays the same.
What it leaves out
The calculator gives the volume of water in a shape. It does not model steps, a bench or a floor with a flat part, and it says nothing about chemicals or safety.
Sources
Questions
How do I find how many gallons are in my pool?
Multiply the length, the width and the average depth in feet to get cubic feet, then multiply by 7.4805. A pool of 24 by 12 feet with an average depth of 4.5 feet is 1,296 cubic feet, which is 9,695 gallons.
Why 7.4805 and not 7.48?
A cubic foot is 1,728 cubic inches and a U.S. gallon is 231, so a cubic foot holds 1,728 divided by 231 gallons, which is 7.4805. With 7.48 the pool above comes to 9,694 gallons, one fewer.
How do I find the average depth of a pool?
Add the depth at the shallow end to the depth at the deep end and divide by 2. That is exact when the floor slopes evenly from one end to the other. A floor with a flat part and a slope is not covered.
How long does it take to fill a pool with a hose?
Divide the gallons by the gallons a minute that your hose delivers. At 10 gallons a minute the pool above takes 969 minutes, which is 16 hours 9 minutes. To find your flow, time a bucket: 5 gallons in 30 seconds is 10 gallons a minute.
Can I measure my pool in meters?
Yes. Choose meters next to the shape and type the lengths and the depths in meters. A pool of 8 by 4 meters that is 1.2 meters deep at one end and 2 at the other holds 51.2 cubic meters, which is 51,200 liters or 13,526 gallons.
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