Swimming Pool Volume Calculator

A swimming pool volume calculator works out how much water a pool holds, in cubic feet and gallons, from its length, width, and depth. It accepts measurements in metric (meters) or imperial (feet) units and updates the result as soon as the dimensions are entered.

Pool volume matters for more than curiosity. It sets how much chlorine or other chemical to add, how much it costs to fill or heat the pool, and how a pump or filter should be sized.

Swimming pool volume formula

A rectangular pool with a flat, uniform bottom is shaped like a box. Its volume is length times width times depth:

$\text{Volume} = \text{Length} \times \text{Width} \times \text{Depth}$

The result comes out in cubic units: cubic feet if the dimensions are in feet, or cubic meters if they are in meters.

To turn that volume into gallons, the calculator applies two fixed conversion factors:

1 cubic meter = 35.3147 cubic feet
1 cubic foot = 7.48052 US gallons

When the dimensions are entered in meters, the calculator first converts each measurement to feet, then multiplies them together. This gives the same answer as converting the finished volume from cubic meters to cubic feet, because the two methods are mathematically equivalent.

How to calculate swimming pool volume

Choose a unit system: metric (meters) or imperial (feet).
Enter the pool's length, width, and depth. For a pool that is deeper at one end than the other, use the average depth (explained below).
Read the volume in cubic feet and gallons. The numbers update automatically.
Use the copy button to copy the result, for example to share with a pool service or record for later.

Worked example (imperial units)

A pool measures 16 feet long, 32 feet wide, and 4 feet deep on average.

$16 \times 32 \times 4 = 2{,}048 \text{ cubic feet}$

$2{,}048 \times 7.48052 = 15{,}320 \text{ gallons}$

Worked example (metric units)

A pool measures 10 meters long, 5 meters wide, and 1.5 meters deep.

$10 \times 5 \times 1.5 = 75 \text{ cubic meters}$

$75 \times 35.3147 = 2{,}648.6 \text{ cubic feet}$

$2{,}648.6 \times 7.48052 \approx 19{,}813 \text{ gallons}$

Pools with more than one depth

Many pools are shallower at one end and deeper at the other. To estimate an average depth for these pools:

Measure the depth at the shallow end.
Measure the depth at the deep end.
Add the two numbers and divide by 2.

For example, a pool that is 3 feet deep at the shallow end and 9 feet deep at the deep end has an average depth of (3 + 9) ÷ 2 = 6 feet. This average-depth method assumes the floor slopes evenly between the two ends. For a pool with a more complex floor, such as a shallow shelf followed by a steep drop, split it into sections, find the volume of each section, and add them together.

Why pool volume matters

Chemical dosing. Chemical products list a dose per volume of water, such as "1 ounce per 10,000 gallons." A pool holding 20,000 gallons needs twice that dose. Using the wrong volume leads to too little chemical, which lets algae or bacteria grow, or too much, which can irritate skin and eyes.

Filling and water costs. Multiplying the pool's volume by the local price per gallon gives an estimate of the cost to fill it, or to replace part of the water during maintenance.

Heating. The energy needed to heat a pool rises with its volume, since more water means more mass to warm. A rough physics rule is that it takes 1 British thermal unit (BTU) to raise the temperature of 1 pound of water by 1°F, and a gallon of water weighs about 8.34 pounds.

Other pool shapes

This calculator is built for rectangular pools with straight sides. Round and oval pools use a different formula, based on the pool's radius rather than its length and width:

$\text{Volume} = \pi \times \text{radius}^2 \times \text{depth}$

For pools with curved edges, steps, or a beach entry, the calculator's rectangular formula gives an approximation. A closer estimate comes from calculating each distinct section of the pool separately and adding the results.

Frequently asked questions

How accurate is a swimming pool volume calculator? For a rectangular pool with a uniform depth, the formula gives an exact volume based on the entered measurements. For a sloped pool, using the average depth gives a close estimate rather than an exact figure. Irregular shapes need a different formula or a section-by-section calculation.

How many gallons are in a cubic foot? One cubic foot holds 7.48052 US gallons of water.

How do I calculate the volume of a round pool? Multiply pi (about 3.14159) by the radius squared, then by the depth: Volume = π × radius² × depth. The radius is half the pool's diameter.

Can this calculator be used for an above-ground pool? Yes. Enter the pool's interior length, width, and depth the same way as for an in-ground pool.

What if the pool has a shallow end and a deep end? Add the shallow-end depth to the deep-end depth and divide by 2 to get an average depth, then enter that as the depth value.

How much water does a typical residential pool hold? Most residential pools hold between 15,000 and 30,000 gallons. A 16-by-32-foot pool with a 4-foot average depth holds about 15,320 gallons. A 20-by-40-foot pool with a 5-foot average depth holds about 29,920 gallons.

How do I convert liters to gallons? Divide the number of liters by 3.78541. For example, 10,000 liters equals about 2,642 US gallons.

Swimming Pool Volume Calculator | Cubic Feet & Gallons