What This Calculator Does
This tool estimates the amount of water a rectangular swimming pool holds, measured in US gallons. By entering the pool's length, width, and average depth in feet, you get an instant volume figure that's useful for dosing chemicals, sizing a heater or pump, and estimating fill costs.
How to Use It
Measure your pool's length and width along the water surface, then determine the average depth. For a pool with a shallow and deep end, average depth equals (shallow depth + deep depth) \(\div\) 2. Enter all three values in feet and the calculator returns the volume in gallons.
The Formula Explained
A rectangular pool's volume in cubic feet is simply length \(\times\) width \(\times\) average depth. Since one cubic foot of water equals about 7.48 US gallons, multiply the cubic footage by 7.48:
$$\text{Gallons} = \text{Length} \times \text{Width} \times \text{Average Depth} \times 7.48$$
Worked Example
Consider a pool 32 ft long, 16 ft wide, with an average depth of 5 ft. The cubic feet $$= 32 \times 16 \times 5 = 2{,}560 \text{ ft}^3.$$ Converting to gallons: $$2{,}560 \times 7.48 = 19{,}148.8 \text{ gallons}.$$
FAQ
Is this US or Imperial gallons? The 7.48 factor gives US gallons. For Imperial gallons, multiply cubic feet by about 6.23 instead.
How do I find average depth? Add the shallow-end depth and deep-end depth, then divide by two.
Why is my actual fill slightly different? Real pools have rounded corners, steps, and varying floor slopes, so this gives a close estimate rather than an exact figure.
