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Pool Volume Calculator: How Many Gallons of Water Does Your Pool Hold?

By Matt Giovanisci | Updated: February 10, 2022

Need to figure out how many gallons of water are in your pool? Just plug in your pool’s measurements into our pool volume calculator below.

Pool Volume Calculator

Pool Volume Calculator Click on your pool shape to calculate the volume of water.
rectangle pool Rectangle
rectangle pool Round

Be sure to measure from the depth of your water, not the height of the wall or the depth of the pool. You want to know how much water is in your pool, and it’s probably not filled up to the top.

Note: The calculator rounds up decimal points, which makes it easier to calculate chemical dosing. But the rounding isn’t enough to throw off your water chemistry calculations.

If you have a more complicated shaped pool, you’ll need to run a few other calculations. We cover how to calculate the volume of an irregular-shaped pool at the end of this guide.

Pool Volume Reference Chart

You can use the pool volume reference chart below to quickly calculate the volume of these common pool sizes.

Note: These are estimates. You’ll always get more accurate results if you measure your pool yourself. And always measure the depth of your water, not the height of your wall.

By the way, if you’re struggling with knowing which pool chemicals to add and when, be sure to check out our Pool Care Video Course. It’s an easy-to-follow guide to help you keep your pool clean and clear.

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How to Calculate Pool Volume Step-By-Step

If you need to calculate the volume of an irregular-shaped pool or you’re still feeling confused, check out our video that walks you through how to calculate the volume of water in your pool. Or keep reading for a complete walk-through on these calculations.

Pool Volume Calculation Basics

To get your pool’s volume, you need to calculate your pool’s surface area and average depth. And to do that, you’ll need a few basic metrics:

Multiply the length and width to get the surface area of a rectangular pool. Then throw in your pool’s depth and you’ll get basic volume calculation.

Another key part of your equation: one cubic foot of water contains 7.5 gallons. So in order to figure out how many gallons your pool holds, you’ll multiply your final cubic foot measurement by 7.5 to find the volume of your pool.

Let’s see what this looks like with different pool shapes.

Rectangular Pool Volume

How you calculate your volume will depend on how the bottom of your pool is laid out.

Constant Depth

The formula for finding the volume of a rectangular pool with one depth (no shallow or deep end) is L × W × D × 7.5 = V (in gallons).

For example, if your swimming pool is 32 feet long, 16 feet wide, and 4 feet deep:

Variable Depths with a Gradual Slope

If your rectangular pool has more than one depth (shallow end, deep end), you’ll need to do a little more math. First, determine the pool’s average depth. Add the shallow end depth to the deep end depth, and divide by 2.

Pool Calculator Rectangle

For example, if your pool’s shallow end is 3 feet, and the deep end is 9 feet, the average depth is 6 feet.

Next, multiply your pool’s length and width and then multiply that number by the average depth. Finally, multiply that figure by 7.5 to calculate the volume of the pool in gallons.

For example, if your pool is 32 feet long, 16 feet wide, and has an average depth of 6 feet:

Variable Depths with a Drop-Off

If 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.

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, simply add them together to determine the volume for the whole pool.

Round or Circular Pool Volume

The formula for finding the volume in gallons of a round pool is 3.14 × r2 × D × 7.5 = V (in gallons)

Start by measuring your pool’s diameter, which is measured at its widest point across (i.e. your pool’s length). Then divide the diameter by 2 to get the radius.

Pool Calculator Radius

Your radius squared is the radius multiplied by the radius. Finally, measure the pool’s depth.

For example, if your pool’s diameter is 18 feet, your radius is 9 feet, and your depth is 4 feet:

Irregular-Shaped Pool Volume

If you have an oval, kidney shape, or other irregular-shaped pool, you can still calculate the volume. You’ll just have to do even more math.

The easiest way to calculate an oddly shaped pool is to imagine it broken down into two or three smaller, regularly shaped parts. Try to see smaller, individual squares, rectangles, or circles within the larger, irregular shape.

Once you’ve mapped them out, measure each part. Then use the same formulae above to calculate the volume in each smaller section. Finally, add all the volume figures together, and you’ll have a pretty close approximation of the pool’s total volume.

When To Ask a Professional to Measure Your Pool

If the swimming pool volume calculator or calculations don’t work properly for you because you have an unusual pool shape, or you just want everything to be more accurate, ask a pool professional to take the measurements and figure out the volume for you.

Remember, before you add any chemicals to your pool water, you need to know how many gallons of water are in your pool. Knowing your pool volume is not only critical for adding the right amount of chemicals, it’s absolutely necessary if you’re installing a new pool pump, pool filter, or pool heater. And keep these calculations handy for future reference. You’ll need them often as a pool owner!

Matt Giovanisci is the founder of Swim University® and has been in the pool and spa industry since 1995. Since then, his mission is to make pool and hot tub care easy for everyone. And each year, he continues to help more people with water chemistry, cleaning, and troubleshooting.
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