Pool Volume Calculator

How the pool volume calculator works

The tool works out the surface area of your pool first, then multiplies that area by the average depth. That gives cubic feet of water. Cubic feet times 7.48 gives US gallons.

Sloped floors are handled by averaging the shallow end and the deep end. If your pool has a sharp drop into a diving well, measure the depth at three or four points and use the middle value for a closer answer.

The formula, step by step

Gallons = Surface Area (sq ft) x Average Depth (ft) x 7.48

• Rectangle area = length x width.
• Round area = 3.14 x radius x radius.
• Oval area = 3.14 x (length / 2) x (width / 2).
• Average depth = (shallow depth + deep depth) / 2.
• Volume in cubic feet = area x average depth.
• Gallons = cubic feet x 7.48. Liters = gallons x 3.785.

Worked example

A rectangle pool is 32 feet long and 16 feet wide. The shallow end is 3 feet and the deep end is 8 feet.

Area = 32 x 16 = 512 square feet. Average depth = (3 + 8) / 2 = 5.5 feet.

Volume = 512 x 5.5 = 2,816 cubic feet. Gallons = 2,816 x 7.48 = 21,065 gallons.

Watch it done

This short video walks through the same job in real life, so you can match what you see on screen to what you do at the pool.

Play video

Tips before you start

Measure at the water line, not the top of the coping, or your total runs high. A 5 percent error on a 20,000 gallon pool is 1,000 gallons, which is enough to throw off a chlorine dose.

Write your final number on the inside of the pump lid or the equipment shed door. You will use it every week during swim season, and it does not change unless you drop the water level.

Pool Volume Calculator FAQs