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Pool Volume Calculator: How Many Gallons Is Your Pool?

Pool Volume Calculator: How Many Gallons Is Your Pool?
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Before you go around adding chemicals into your pool, you need to know the pool volume calculation basics to know how much you need to use. The more water it holds, the more you’ll need. Following your manufacturer’s instructions is the smartest idea, but you will need to know how much water your pool needs to do this.

If you’re reading this article, then there’s a high probability that you want to know how to calculate your pool’s volume. Well, estimating the volume by eye is impossible, so you need to calculate how many gallons of water it holds.

Keep reading, and we will show you how!

What Is a Pool Volume Calculator?

Maintaining your pool can be difficult. It’s important to know the amount of chemicals, specifically chlorine, pH increase, shock, and any other chemicals to use for pool care that you need to put, you would have to know the water volume. If you don’t have a rectangular or circular pool, you must plug the measurements into a mathematical formula to get the volume.

But if you’re not proficient in math, you can plug those numbers into a pool calculator and let it do the work. A pool volume calculator is an efficient tool to calculate pool volume or calculate gallons in pool capacity. Before you use this tool, you must measure the depth of the water using a pool water calculator instead of the height of the wall. Complex shaped pools require multiple calculations to calculate the number of gallons the pool holds.

How a Pool Volume Calculator Works

You need to know some basics before you can calculate the pool volume. The basic elements include area, length, width, depth, height, volume, radius, diameter, and pi (3.14 constant). So if you don’t remember the basics, here’s a quick recap.

The area of a rectangle or square is length x breadth

The area of a right triangle is length x width divided by 2

And the area of a circle is pi x r2

To calculate cubic volume, you will require the pool’s depth and the surface area. And to make sure these calculations are accurate, you need to divide your pool into sections by depth (deep end and shallow end).

Another important part of your equation is one cubic foot of water has 7.5 gallons. So, to determine the total number of gallons the pool holds, you will have to determine the cubic feet measurement of your pool and then multiply the number by 7.5 to get the volume.

Once you have done these steps, you have to plug the numbers. If it’s still confusing, you should look at a pool care video course.

How to Calculate Pool Volume

How Many Gallons Is My Pool?

To find out the volume of your pool, you’ll have to find the pool dimensions and apply various formulae. The shape of the pool also plays a main part in getting to know the number of gallons required. Here are the solutions to finding your pool volume.

It’s important to calculate this number if you plan on having pool water delivered. Most companies want to know approximately how many gallons you will nee

Constant Depth Square/Rectangle Pool

A Rectangular swimming pool is one of the most common types of swimming pools. If you have

Length x width x depth x 7.5 = volume

You can find the surface area of the pool by multiplying the length and width. Multiplying that by the depth will result in volume in cubic feet. As there are 7.5 gallons in each cubic foot, multiply the cubic feet of the pool by 7.5 to find the volume of the pool.

Irregular Shapes (Sloped, Drop-Offs, etc.)

Kidney Shaped Pool or Irregular Shaped Pool

Not all pools are rectangular or round; some of them have irregular fancy shapes. You can use two methods to find the capacity of an irregular pool shape. Imagine the pool as a combination of regular shapes and find out the various areas before adding them to determine the total capacity.

0.45 x (A+B) x length x average depth x 7.5 = volume (in gallons)

The total measurement A + B multiplied by 0.45 multiplied by the length will give you the surface area of the kidney shape. Try this calculation:

0.45 x (A+B) x length x average depth x 7.5 = volume (in gallons)

0.45 x 18 ft x 25 ft x 5 ft x 7.5 = 7593.75 gallons

Parts Per Million (ppm)

One of the most important calculations you use is parts per million. The amount of liquids and solids in the water is measured in parts per million, as in three parts of chlorine in every single million parts of water, or 3 ppm.

Here is a list to show common terms with equivalents.

Cubic foot (cu. ft.) = 12 inch wide x 12 inch long x 12 inch high

One cubic foot of water contains 7.48 gallons and weighs 62.4 pounds

One gallon of water weighs 8.33 pounds

One part per million (ppm) represents 8.3 pounds of chemical per million gallons of water

Although, one gallon of chlorine, for example, poured into one million gallons of water doesn’t equal one ppm. This is due to the two liquids not having equal density.

Variable Depths With a Gradual Slope

If your swimming pool has variable depth (shallow end, deep end), you will have to do more math to calculate the volume using the pool gallon calculator.

Determine pool measures like the pool’s average depth (add the shallow end depth and deep end depth before diving by 2).

(shallow end’s depth + deep end’s depth) ÷ 2 = average D (in feet)

For example, let’s assume your pool’s shallow end is 3 feet and the deep end is 9 feet.

(3 + 9) ÷ 2 = 6 feet (average depth)

After this, calculate the length and width to calculate the surface area of the pool. Multiply this number by average depth to calculate the volume in cubic feet. After this, find the product of that figure by 7.5 to calculate the volume of the pool in gallons.

If your pool is 32 feet long, 16 feet wide, and has an average depth of 6 feet, then:

32 × 16 × 6 × 7.5 = 23,040 gallons

Variable Depths With a Drop-off

If, instead of a gradual slope down to the deep end, your pool has a definitive drop between the shallow and deep ends, the average depth will be different, even if the shallow end and deep end are still, for example, 3 feet and 9 feet, respectively.

It may be easier, in this case, to treat the shallow and deep ends as separate pools. This will allow you to apply the volume of each section using the constant depth formula.

Once you have the volumes of both parts, add them together to determine the volume for the whole pool.


Circular Pool

Round is one of the most popular pool shapes, and to find out the amount of water you need to fill in your circular swimming pool, you need to find out the round pool volume. The formula for the circular pool water volume calculator is as follows:

3.14 x radius squared x average depth x 7.5 = volume in gallons.

3.14 refers to pi, which is a mathematical constant. The radius equals one-half the diameter, so measure the distance along the broadest part of the round or oval pool and divide it in half at the radius. Multiply the radius by itself to find them after you measure the radius.

Use the hot tub as an example to calculate the volume of a round container. The diameter of the tub is 10 feet, and half of it is 5 feet. For squared radius, you need to multiply 5 feet by 5 feet to get 25 square feet. After this, you can return to the formula.

3.14 x radius squared x average depth x 7.5 = volume (in gallons)

3.14 x 25 ft x 3 ft x 7.5 = 1766.25 gallons

Understanding Pool Volume Calculator Formula Variables


The area is a quantity that expresses the extent of a two-dimensional region or shape. In contrast, the surface area is its analog on the two-dimensional surface of a three-dimensional object.


Length is a measure of distance used to calculate the area and surface area of your swimming pool.


Width is the horizontal measurements taken at right angles of the length. It also is the largeness of the extent or scope of a figure.


This is the measurement of your swimming pool from head to foot or from base to top.


A straight line from the center to the circumference (border) of a circle or sphere is the radius.


A straight line from one end of a circumference to the other is called the diameter. You can multiply the radius by two to find the diameter.


Pi is the ratio of the circumference to the diameter. It’s a constant, 3.14, approximately.

The Bottom Line on Pool Volume Calculators

You can now let your pool volume calculator calculate how many gallons of water you require to fill your swimming pool. The instructions above will help you decide the correct amount of chemicals to add to your pool to keep it nice and clean.