How To Calculate Pool Volume

Like a cook who needs to know how much of each ingredient to add to a dish, pool owners need to know how much of their maintenance products they need to add to their water. In order to do this properly, pool owners must know their pool volume — how much water is actually in their pool.

Calculating your pool volume is essential to correctly balancing the water. Making only rough estimates can result in errors and end up causing issues. Over-estimating is a waste of money; under-estimating will result in unsanitary water. If the volume of your pool isn't in the original documentation, it's easy to calculate it yourself.

Running The Numbers

Three average measurements are used to calculate pool volume for most pools: length, width, and depth. There are more complicated formulas for measuring oddly-shaped pools, but most of them also include these measurements.

If your pool has a shallow end and a deep end, you'll need to measure both in order to find the average depth. For example: The shallow end is 3' deep and the deep end is 8'. Using the Average Depth formula: (3+8)÷2=5.5' Average Depth.)

As you'll notice below, most of these formulas are multiplied by 7.5, which is approximately how many gallons are in a cubic foot. The pool size measurements will help you find the cubic footage of the pool, and multiplying this by 7.5 will help you find a close estimate of volume in gallons.

Once you have this number, you should be able to apply the correct amount of pool chemicals to your pool water and avoid any future dosage issues.

The combined formulas should look like this:

Square and Rectangle Pools:

Length x Width x Average Depth x 7.5 = Approximate Volume (Gallons)

Round Pools:

3.14 x Radius x Radius x Average Depth x 7.5 = Volume (Gallons)

The Radius equals the diameter divided by 2. (Example: A 16' diameter divided by 2 = 8' radius.)

Note: Most round pools have a single depth.

Oval Pools:

3.14 x Length x Width x .25 x Average Depth x 7.5 = Approximate Volume (Gallons)

Kidney-Shaped Pool:

(A + B) x Length x 0.45 x Average Depth x 7.5 = Approximate Volume (Gallons)

Note: “A” and “B” measurements are the two widest points of the kidney shape.

Irregular Shapes or Free-Form Pools:

Longest Length x Widest Width x Average Depth x 5.9 = Approximate Volume (Gallons)

Quick Reference

For your convenience, you can also consult the following charts. They detail the volume of many popular pool sizes.

Above Ground Pool Volume (48″ Wall Height)

Pool Size	Gallons
15′ Round	5,300
18′ Round	7,600
20′ Round	9,400
24′ Round	13,600
27′ Round	17,200
28′ Round	18,500
11×25 Oval	6,500
11×30 Oval	7,800
15×25 Oval	8,900
15×30 Oval	10,600
18×33 Oval	14,000
18×38 Oval	16,100

Above Ground Pool Volume (52″ Wall Height)

Pool Size	Gallons
15′ Round	5,800
18′ Round	8,300
20′ Round	10,200
24′ Round	15,300
27′ Round	18,600
28′ Round	20,000
11×25 Oval	7,000
11×30 Oval	8,400
15×25 Oval	9,600
15×30 Oval	11,500
18×33 Oval	15,200
18×38 Oval	17,500

In-Ground Pool Volume (Standard Depth)

Pool Size	Gallons
12×24 Rectangle	10,800
16×32 Rectangle	19,200
16×36 Rectangle	21,600
18×36 Rectangle	24,300
20×40 Rectangle	30,000
16×32 Oval	17,200
18×36 Oval	21,700
18×36 Oval	21,700
20×40 Oval	26,800
17×33 Grecian	19,700
17×37 Grecian	22,200
20×36 Grecian	24,300
20×44 Grecian	30,300
16×30 Kidney	14,900
16×34 Kidney	16,500
20×38 Kidney	20,200

For more information on pool size or chemical usage, check our complete blog library, or reach out to one of our knowledgeable staff members at your local Leslie's. At Leslie's, your pool is our passion.