Pool Volume Calculator – Here to Make Your Pool Care Simpler

Multiple pool care maintenance routines require you to know your pool volume. Maybe you’re adding pool chemicals, refilling your pool, or calculating your pool turnover; you need pool volume to accomplish them.

It’s become a real hassle for most DIY maintainers who want to maintain their pools without hiring an expert. Without a way to calculate the pool volume, most pool owners end up hiring a pool expert. If you want to DIY all the pool maintenances, you might want to know how to calculate your pool capacity.

I get it if you fear the numbers and all the math, but in this post, I’m giving you the option of entering the measurements and get the capacity instantly if you fear the mind tormenting calculations. I’m also giving out the formulas I used in building the calculators for those who love curiosity. Let’s get started.

How to Calculate Pool Volume

Getting the accurate pool volume is necessary, and this post will help you find the capacity of your rectangular, rounded, triangular, and even irregular-shaped pools. Which one is yours?

Where do you start? The best part to start is to find the surface area of the pool top and multiply it with your pool’s average depth, and you’ll get the pool capacity.

Yes, it’s as easy as it sounds, but there are two or three things you have to keep in mind. Let’s get started.

Pool Volume Calculation Basics

When calculating the volume, there are terms that you will want to know and letters you might come across that I used to shorten the formulas. They include:

AAreaArea of the pool top
VVolumeThe capacity of the pool
LLengthDistance of the longest side of your pool
WWidthDistance of the shortest side of your pool
DDepthHow deep your pool is
ADAverage DepthDeep end depth plus shallow end depth divided by 2
HHeightHeight of your above ground pool from the ground to its top
rRadiusThe distance between one point of a round pool to its center
dDiameterThe distance between two points of a round pool directly across its center
3.14 or 22/7π (pi)Pi constant used in calculating the area of round shapes

Basic Formulae to Use When Calculating Pool Volume

Here are the formulae you will be using here:

Area of a Rectangle or Square: A = L × W
Area of a Triangle (Right): A = (L × W) ÷ 2
Area of a Circle: A = Pi × r2
Volume: V = Area x Depth (A x D)

Since you’re dealing with feet, your pool volume will be in a cubic foot. You will need to convert the value to gallons – the most used capacity unit in pool care.

One cubic foot of water equals approximately 7.5 gallons. That means, to get how many gallons of water your swimming pool holds, you need to multiply the pool volume in cubic feet by 7.5.

Volume (cubic feet) x 7.5 = Volume (gallons)

Calculating the Volume of Rectangular or Square Pool

Rectangular or square-shaped pools are of two types:

  • With uniform depth
  • Variable depths and gradual slope (the most common)

The formula and method of calculating their volumes are different.

With Constant Depth

If your swimming pool has one uniform depth, measure its length and width. Multiply the two to find its surface area. Measure the depth and multiply it with the surface area to get its volume in cubic feet.

If there no markings of how deep the pool is, which is rare, you can use your leaf net telescope pole to mark how deep the pool is and then use a tape measure to measure the distance between the markings.

Length (L) × Width (W) = Surface Area (in square foot)
Area (A) x Depth (D) × 7.5 = Volume (in gallons)

In an example: Assuming your swimming pool is 40 feet long, 20 feet wide and 3.5 feet, its volume would be:

40ft x 20ft = 800ft2
800ft2 x 3.5ft = 2800ft3
2800ft3 x 7.5 = 2100 Gallons

40ft x 20ft x 3.5ft x 7.5 = 2100 Gallons

With Variable Depths and Gradual Slope

If your swimming pool has a deep end and deep end, your swimming pool has variable depths and a gradual safety slope. For such a pool, you’ll do some more calculations.

Start by getting your pool’s length and width. Get the deep end depth (marked on the deep end pavement) and the shallow end depth (marked on the shallow end pavement).

Remember the formula for a rectangle or square? Here the depth will be the average depth. How do you get it?

[Depth (deep end) + Depth (shallow end)] / 2 = Average Depth

Assuming your pool’s deep end depth is 4 feet, and the shallow end is 3 feet, then its average depth is:

(4+2) ÷ 2 = 3 feet

Using the formula you used for a rectangular-shaped pool with uniform depth, replace D with average depth.

Length (L) × Width (W) x average Depth × 7.5 = Volume (in gallons)

In an example: assuming the depths remain as assumed above but the length is 40ft, and width is 20ft, your pool volume would be:

40ft x 20ft x 3ft x 7.5 = 2100 Gallons

With Variable Depth and a Drop Off

If your swimming pool has variable depths and a drop-off, though rare, the formula is different. The best approach here would be to treat each section (deep and shallow) as two other rectangular or square pools depending on the length and width. Get their volumes and add them to get the total.

An example: Your swimming pool is 45ft long and 35ft wide. The shallow end depth is 2ft, and the deep end 4ft. Measure the distance from when the drop is to both ends dividing the length into two sections. We can assume the length from the deep end to the drop-off is 25ft, and the distance from the drop-off to the shallow end is 20ft.

That would mean you have:

Volume of the deep end = 25ft x 35ft x 2ft x 7.5 = 31,125 Gallons
Volume of the shallow end = 20ft x 35ft x 2ft x 7.5 = 10,500 Gallons

So, your total pool capacity = 31,125 + 10,500 = 41,625 Gallons

Calculating the Volume of a Round Pool

A round pool can either have a perfectly circular top or an oval-shaped top. Whichever the case, the formulae are similar:

Pi x square of its radius x depth x 7.5 = volume in gallons
3.14 x r2 x D x 7.5 = Volume

To get the radius, you will need to measure the diameter, divide it by two, and squares it; you multiply the value of r by itself.

r = d ÷ 2
r2 = r x r

Assuming the diameter of your swimming pool is 30ft, then its radius would be:

30ft ÷ 2 = 15ft (radius)
15ft x 15ft = 225ft2(r2)

Now measure how deep the pool is from the surface to the ground using a tape measure. Once you have your pool’s depth, you can now calculate its volume using the original formula:

Pi (π) x square radius (r2) x Depth (D) x 7.5 = Volume (Gallons)
3.14 x r2 x D x 7.5 = V (Gallons)

Assuming our depth is 4ft deep, the volume of our above-ground pool would be:

3.14 x 225ft2 x 4ft x 7.5 = 21,195 Gallons

Calculating the Volume of an Irregularly Shaped Pool

Remember, not all swimming pools have perfect rectangular, square, or round shapes; some are available in oval and kidney shapes. There are even other complex pool shapes that you might come across, while others come with a pool end that mimics a natural shoreline.

Their volume calculations are more complex than the above. You have to do more math to get the pool capacity. The best move is to draw a small representation on paper and use a ruler to break it down into small, regular shapes.

Calculate the area of these shapes and then multiply with their depth. If the shape has two depths, then find the average. Add all the volume you’ve got to get the total volume, which is your pool’s capacity.

If this turns out to be too much for what you signed for, hiring a professional would be the best. You could stay and see as the expert calculate the volume so that you can do it yourself next time.


Pool volume has never been an issue for many pool owners until they decide to take care of the swimming pool themselves. If you are adding water, chemicals or refilling your swimming pool, you will want to know the amount of water your swimming pool holds. And this post will be here waiting for you; it simplifies the whole process. The simple-click volume calculator can even save you time, and it’s much convenient if you don’t want to do all the calculations.

About the author

Sharif Miah

Hi! I'm Sharif, the founder of Globo Pool® and I have been working in the pool & hot tub industry for the last few years. I love to share my experiences with people & hope you are enjoying my information and lessons!

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