Work out how many gallons your pool holds, and the surface area you need when sizing a robotic pool cleaner. Pick a shape, enter your measurements, and the numbers update as you type. Nothing is stored and nothing is sent anywhere.
1. Pool shape
2. Measurements
How to measure your pool
Two mistakes account for most wrong answers. The first is measuring the wall height instead of the water depth: pools are almost never filled to the top, and a 52 inch wall usually holds around 46 inches of water. The second is using the outside dimensions of an above ground pool rather than the inside of the liner.
For a pool with a shallow end and a deep end, tick the slope box and enter both depths. The calculator averages them, which is accurate for a pool with an even slope and close enough for most others.
The formulas
Every figure here comes from standard geometry. There is nothing proprietary, so you can check the result by hand.
- Rectangle: length × width × average depth × 7.48
- Round: π × (diameter ÷ 2)² × average depth × 7.48
- Oval: π × (length ÷ 2) × (width ÷ 2) × average depth × 7.48
- Kidney or freeform: length × width × 0.85 × average depth × 7.48
The 7.48 is US gallons per cubic foot. Multiply cubic feet by 28.32 instead for litres. Kidney and freeform shapes vary too much for an exact formula, so the 0.85 factor is the standard approximation the pool industry uses.
Why surface area matters more than gallons for a robot
Gallons is the number you need for chemicals. It is not the number you need for a robotic pool cleaner.
Robot manufacturers rate coverage in surface area, because what limits a cleaning cycle is how much floor the machine has to travel, not how much water sits above it. A deep pool and a shallow pool with the same footprint take a robot roughly the same time to clean, but hold very different volumes.
So when you compare a cleaner rated for 1,600 sq ft, compare it against the surface area figure above. Then check run time separately, because a robot can be rated for your pool size and still need two cycles to finish if the battery is small.
Frequently asked questions
How many gallons is a 24 foot round pool?
At 4 feet of water depth, roughly 13,500 US gallons. At 4.5 feet, closer to 15,200. Depth changes the answer significantly, which is why measuring the water rather than the wall matters.
How many gallons is a 16 by 32 foot rectangular pool?
With an average depth of 5 feet, around 19,100 US gallons. Enter your own depth above for an accurate figure.
Do I measure the wall height or the water depth?
The water depth. Pools are filled to somewhere below the top of the wall, usually to the middle of the skimmer opening. Using wall height will overstate your volume by ten percent or more.
How accurate is this calculator?
For rectangular and round pools with an even floor, it is exact geometry. For sloped floors it averages the two depths, which is accurate for an even slope. Kidney and freeform pools use the industry standard 0.85 approximation and should be treated as close rather than precise.
What size robotic pool cleaner do I need?
Match the robot's rated coverage in square feet to the surface area figure above, then check run time against how much debris your pool collects. See our robotic pool cleaners for coverage ratings on each model.
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