Pool volume calculator
Updated:
Every chemical dose scales with your pool’s volume, so getting the gallons right matters most. Enter your pool’s shape and dimensions to estimate it.
How to calculate pool volume
Volume is surface area times average depth, converted to gallons. For a rectangle it is length × width × average depth × 7.48, because a cubic foot holds 7.48 US gallons. Round pools use about 5.9 and oval pools about 6.7 instead of 7.48, because their surface is smaller than the rectangle around them. Average depth is your shallow and deep depths added together and divided by two.
Why volume matters so much
Every dose in the chemistry calculators scales directly with volume. A 20% error in gallons is a 20% error in every chemical you add, so measure carefully and round honestly. If your pool is an unusual shape, split it into sections, estimate each, and add them up.
Measuring tips
Measure length and width at the water line, not the deck. For average depth, take the shallow-end and deep-end depths and average them. For a round pool, the diameter is the distance straight across the middle.
How the volume is calculated
Measure in feet or meters. The calculator multiplies length, width and average depth, scales by how much of that rectangle the shape covers, then converts to gallons or liters.
Rectangle
gallons = length × width × average depth × 7.48
NIST gives a cubic foot as 0.02831685 m³ and a US gallon as 0.003785412 m³, so a cubic foot holds 7.48 gallons. A 32 × 16 ft pool that runs from 3 ft to 7 ft deep holds about 19,150 gallons.
Measuring in meters
liters = length × width × average depth × 1,000
A cubic meter is exactly 1,000 liters. Round pools use 785 (π/4 × 1,000) and ovals 896 in place of 1,000.
Round
gallons = diameter × diameter × average depth × 5.875
A circle covers π/4 of the square around it, and the calculator uses π/4 exactly: π/4 × 7.48 = 5.875. That is where the common rule-of-thumb factor of 5.9 comes from.
Oval
gallons = length × width × average depth × 6.7
The calculator counts an oval as 89.6% of the rectangle around it, the share a straight-sided pool with half-round ends covers when it is about twice as long as it is wide. 0.896 × 7.48 = 6.7.
Average depth
average depth = (shallow + deep) ÷ 2
A pool 3 ft deep at one end and 7 ft at the other averages 5 ft.
Frequently asked questions
How do I find my pool’s volume in gallons?
Multiply length × width × average depth (in feet) by 7.48 for a rectangle. Round pools use about 5.9 and ovals about 6.7. This calculator does it for you in gallons and liters.
What is the average depth?
Add your shallow-end depth and deep-end depth and divide by two. A pool that is 3 ft shallow and 7 ft deep has an average depth of 5 ft.
How accurate is this estimate?
It is close for standard shapes. Irregular or kidney-shaped pools vary, so treat the result as an estimate, start chemical doses conservatively, and re-test.
Sources
- NIST Special Publication 811, Appendix B.8: conversion factors. Cubic foot and US gallon definitions behind the 7.48 factor
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