Pool Volume Calculator

What Is the Pool Volume Calculator?

The pool volume calculator estimates how many gallons or liters of water are needed to fill a swimming pool of given dimensions, plus the weight of that water. Choose a rectangular or circular pool, switch between imperial and metric units, enter width, length, and depth or the diameter, and the tool returns the volume instantly.

Volume is the number behind nearly every pool chore: chemical dosing, pump sizing, filter turnover, heating time, and the water bill for a refill. Getting it wrong makes chlorine guesses dangerous and heater runtimes mysterious, which is why accurate measurement is worth ten minutes with a tape.

The Formulas for Rectangular and Circular Pools

For a rectangular pool, volume equals length times width times average depth, converted to gallons by multiplying cubic feet by 7.48. In metric, cubic meters become liters directly, since one cubic meter holds 1000 liters.

For a circular pool, multiply pi by the radius squared by the depth. A round above ground pool with a 12 foot diameter and a 4 foot depth holds about 3390 gallons. In any shape, the critical input is average depth, not wall height: a pool with a shallow 3 foot end and a deep 6 foot end averages 4.5 feet, and filling to the skimmer rather than the brim shaves a few inches off every measurement.

Step by Step: Measuring Your Pool

Measure length and width at water level, not at the deck coping, and for freeform shapes approximate with the longest dimensions. For depth, measure the shallow end and the deep end from the water surface to the floor, then average the two readings.

Enter the numbers in your chosen unit system, run the calculation, and note both the volume and the water weight, since a filled backyard pool weighs tens of thousands of pounds, which matters structurally for above ground models placed on decks or slopes.

Why Calculators Handle Regular Shapes Best

This calculator supports rectangular and circular pools, which cover the vast majority of installations. Kidney shapes, L shapes, and beach entry pools need decomposition into rectangles and circles or measured fill in stages, because a single averaged formula underestimates the bulges.

Whatever the shape, remember that the true fill volume is measured to the operating water level. Two or three inches below the tile line on a 20 by 40 foot pool is roughly 2000 gallons of difference, so measure what is actually there before dosing chemicals.