How to use this calculator
Select your pool shape, enter the dimensions in feet, and provide the depth. You can enter the shallow and deep end separately (the calculator averages them) or enter a known average depth directly.
Optionally, adjust the hose flow rate and enter your local water rate to see fill time and cost estimates. The default flow rate of 9 gallons per minute is typical for a standard 5/8 inch garden hose at normal residential water pressure.
Pool volume by shape
Rectangle: The simplest calculation. Multiply length by width by average depth, then multiply by 7.48 to convert cubic feet to gallons. Most common for lap pools and traditional backyard pools.
Round: Uses the radius (half the diameter) squared times pi times the average depth, then the 7.48 conversion factor. Common for above ground pools and spas.
Oval: Uses a modified formula with a 5.9 multiplier that accounts for the curved ends. Multiply length times width times average depth times 5.9 to get gallons directly.
Kidney: Measure the width at both the wide end (A) and narrow end (B), plus the overall length. The formula averages the two widths and applies a 0.45 shape factor to approximate the curved area.
Frequently asked questions
How do I measure the average depth of my pool?
Measure depth at the shallow end and the deep end, then add them together and divide by two. For pools with a consistent flat bottom, measure at any point. If your pool has a distinct diving area, consider calculating that section separately for a more accurate total.
How long does it take to fill a swimming pool?
A standard garden hose delivers about 9 gallons per minute, or 540 gallons per hour. A typical 15,000 gallon pool takes roughly 28 hours to fill with one hose. Two hoses cut the time in half. Some utilities offer bulk water delivery by truck, which can fill a pool in one to two hours.
How many gallons are in a standard swimming pool?
It depends on size. A small pool (10 by 20 ft at 5 ft deep) holds about 7,500 gallons. A mid-size pool (15 by 30 ft at 5 ft) holds about 17,000 gallons. A large pool (20 by 40 ft at 5.5 ft) holds around 33,000 gallons.
Why does pool volume matter for chemicals?
Chemical dosing is calculated per gallon. Underestimating your pool volume leads to under-dosing (algae, bacteria), while overestimating leads to over-dosing (skin irritation, equipment damage). An accurate volume measurement is the foundation of proper pool chemistry.