Pool Volume Calculator
Enter your pool dimensions to get the volume in gallons and liters, plus the pump turnover it needs. This is the number every chlorine, salt, and chemical dose is based on, so get it right once.
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US gallons
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liters
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GPM (8 hr turnover)
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avg depth (ft)
This is your dosing number. Use gallons for every chemical calculation:
Right-sized gear for a -gallon pool
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How to Calculate Pool Volume
Pool volume is surface area times average depth, converted to gallons. For a rectangular pool, surface area is length times width. For a round pool it is pi times the radius squared, and for an oval it is pi times the two radii. Multiply the surface area by the average depth in feet to get cubic feet, then multiply by 7.48 to get US gallons. To convert to liters, multiply gallons by 3.785.
Use Average Depth, Not the Deep End
Most pools slope from a shallow end to a deep end, so a single depth reading overstates the volume. Average the shallow and deep depths first. A pool that is 3 feet at the shallow end and 8 feet at the deep end has an average depth of 5.5 feet, not 8. Using the average is what keeps your gallon count, and therefore every chemical dose, accurate.
Volume Drives Every Dose and the Pump
Once you know your gallons, the rest of pool care follows. Chlorine, salt, stabilizer, acid, alkalinity increaser, and shock are all dosed per gallon, so an accurate volume makes every calculation on this site quick and correct. Your pump and filter are sized to turn the water over in about 8 hours, which the tool above estimates for you. Write your gallon number down somewhere you will not lose it.
Now dose to your number:
Frequently Asked Questions
How do I calculate the volume of my pool in gallons?
For a rectangular pool, multiply length by width by average depth in feet, then multiply by 7.48, since there are 7.48 US gallons in a cubic foot. For example, a 32 by 16 foot pool with an average depth of 5 feet holds about 19,150 gallons. Round pools use the circle area (pi times the radius squared), and oval pools use the two radii. This calculator handles all three shapes and lets you enter a shallow and deep end so it uses the true average depth.
What is average depth and how do I find it?
Average depth is the mean of your shallow end and deep end depths. If your shallow end is 3 feet and your deep end is 8 feet, your average depth is 5.5 feet. For a pool with a constant depth, the average is just that depth. Using average depth, not the deep end, is what keeps your gallon estimate accurate, which matters because every chemical dose is based on your true volume.
Why does pool volume matter so much for chemicals?
Every chemical dose, chlorine, salt, stabilizer, acid, alkalinity, and shock, is calculated per gallon. If your volume estimate is off, every dose is off in the same direction, which wastes chemicals or leaves your water unbalanced and unsafe. Getting an accurate gallon count once, and writing it down, makes every future dosing calculation quick and correct.
How accurate is a calculated pool volume?
For a standard rectangular, round, or oval pool with a known shape, a calculated volume is usually within a few percent of the true number, which is plenty accurate for dosing. Irregular or free-form pools, kidney shapes, and pools with attached spas or tanning ledges are harder to estimate, so for those it is reasonable to break the pool into sections, calculate each, and add them up.
What size pump do I need for my pool volume?
A common target is to turn over your entire pool volume in about 8 hours. Divide your gallons by 8 to get the gallons per hour, then by 60 to get the gallons per minute your pump and filter should move. A 20,000 gallon pool wants roughly 2,500 gallons per hour, or about 42 gallons per minute. This calculator estimates that target for you once you enter your dimensions.