Pool Volume Calculator

How pool volume is calculated

Every shape is a surface area times an average depth, converted at 1 cubic foot of water = 7.48052 US gallons:

Rectangular: length × width × average depth
Round: π × radius² × average depth
Oval: π ÷ 4 × length × width × average depth — an oval is an ellipse, so it holds about 78.5% of what the same-sized rectangle would

Average depth is the key input. For a pool with a sloped floor, average the shallow and deep ends: a pool that runs 3 ft to 8 ft has an average depth of (3 + 8) ÷ 2 = 5.5 ft. Use the water depth, not the wall height — water normally sits a few inches below the rim. For free-form or kidney pools, the rectangular formula with your best length and width gives a usable estimate; pros often multiply that result by about 0.85 for the curves.

Why it matters: chemical dosing, salt for a salt-water generator, heater and pump sizing, and fill cost are all based on gallons. A 10% volume error becomes a 10% chemical error, so a careful average-depth measurement is worth more than a fancy formula.

Frequently asked questions

How long will it take to fill? Divide the gallons by your hose's flow: a typical garden hose delivers 5–10 gallons per minute (measure yours by timing a 5-gallon bucket). A 19,000-gallon pool at 8 gpm takes roughly 40 hours.

Above-ground round pools? Use the round shape with the water depth — usually the listed wall height minus about 6 inches. A "24 ft × 52 in" pool holds its water about 4 ft deep.

Gallons or liters? US pool chemicals are dosed per gallon; metric labels per liter. Both are shown above — 1 US gallon = 3.78541 liters.