Pool Volume Calculator
A free pool volume calculator. Pick your pool shape, enter the dimensions and depth, and get your pool volume in gallons and liters for chemical dosing, salt, and heater sizing.
This free pool volume calculator estimates your pool in gallons and liters from its shape, dimensions, and average depth, covering rectangle, oval, round, and kidney or irregular pools.
Your pool volume
Kidney and irregular shapes are estimates, round up when dosing chemicals. See Terms of Use.
Why pool volume matters
Almost every pool decision starts with the gallon count. Chlorine, algaecide, and shock are all dosed in parts per million, which means the amount you add depends entirely on how much water the dose spreads through. Guessing at the volume is how pools end up under-dosed and green, or over-dosed and irritating. A 20,000 gallon pool and a 15,000 gallon pool can look the same from the deck, but a chemical kit sized for one will fail in the other.
Salt systems are even more volume-sensitive. A saltwater generator converts dissolved salt into chlorine at a target of roughly 3,000 to 3,400 ppm, and the pounds of pool salt you buy come straight from the gallon math. Salt pounds equal gallons times 8.35 times the ppm increase divided by one million, so a 5,000 gallon error changes the salt bill by more than 100 pounds. Get the volume right once and every salt top-up after that is simple.
Heater sizing runs on volume too. Heating a pool is raising thousands of gallons by several degrees, and the BTU rating needed depends on how many gallons and how fast you want the temperature to rise. The same logic applies to pump and filter sizing: turnover rates assume the full volume cycles through the filter in a set number of hours. Undersized equipment runs longer, wears faster, and costs more in electricity.
Finally, the gallon count prices a drain-and-refill and sets expectations for evaporation top-ups. Use this calculator, note the average depth from your shallow and deep ends, and keep the number somewhere handy. It is the one figure your pool store will ask for every visit.
Pool volume calculator questions
How do I calculate my pool volume in gallons?
Pick your shape, then use the matching multiplier. Rectangle: length times width times average depth times 7.48. Oval: length times width times average depth times 6.7. Round: diameter squared times average depth times 5.9. Kidney or irregular pools use a rectangle estimate times 7.0 and should be treated as approximate.
How do I find my pool's average depth?
Add the shallow end depth to the deep end depth and divide by two. If your pool has a gradual slope rather than two flat levels, take several depth readings across the pool and average them instead.
How much salt does my saltwater pool need?
Salt pounds equal gallons times 8.35 times the ppm increase divided by 1,000,000. For example, raising a 20,000 gallon pool by 2,500 ppm takes about 417 pounds of pool salt. You need an accurate gallon count first, which is what this calculator gives you.
How many liters are in my pool?
Multiply gallons by 3.785 to get liters. A 20,000 gallon pool holds about 75,708 liters. The calculator above shows both automatically.
What is the formula for a kidney shaped pool?
Measure the overall length and width as if it were a rectangle, multiply by the average depth and by 7.0. That multiplier trims the rectangle volume to account for the curved shape. It is an estimate, so round up when buying chemicals or salt.