How the pool gallons calculator works
Gallons come from cubic feet. One cubic foot of water is 7.48 US gallons, so the tool multiplies your pool footprint by the average water depth and then applies that factor.
Shape matters more than most owners expect. A round pool holds about 21 percent less water than a square that fits around it, so picking the right shape keeps your dosing honest.
The formula, step by step
Gallons = Length x Width x Average Depth x 7.48 x Shape Factor
- Rectangle shape factor is 1.0.
- Round and oval shape factor is 0.785 (that is 3.14 divided by 4).
- Kidney and freeform pools sit near 0.85.
- Multiply length, width, average depth, 7.48 and the shape factor.
Worked example
An oval above ground pool is 24 feet long, 12 feet wide, with 4 feet of water.
24 x 12 x 4 = 1,152 cubic feet before the shape factor.
1,152 x 0.785 = 904 cubic feet. Gallons = 904 x 7.48 = 6,764 gallons.
Watch it done
This short video walks through the same job in real life, so you can match what you see on screen to what you do at the pool.
Tips before you start
Fill lines matter on above ground pools. A 52 inch wall almost never holds 52 inches of water, so measure from the floor to the water line with a pole and a tape.
Once you know your gallons, most chemical math turns into simple multiplication. Salt, chlorine, stabilizer and alkalinity products all list a dose per 10,000 gallons.
Pool Gallons Calculator FAQs
How many gallons is a 24 foot round pool?
A 24 foot round pool with 4 feet of water holds about 13,500 gallons. Drop your real water depth into the calculator for an exact figure.
How many gallons is my pool if the depth changes?
Use the average of the shallow and deep measurements. That single average depth gives a gallon count within a few percent for most residential pools.
Is a gallon the same everywhere?
No. This tool uses US gallons. An imperial gallon is about 1.2 US gallons, so check your product label if you buy chemicals outside the US.
Why does my pool store give a different number?
Stores often quote the manufacturer rating, which assumes the pool is filled to the very top. Real water levels sit lower, so your number is usually smaller.