So you’ve purchased a pool. And it’s a pretty cool thing to see in your backyard. Whether it’s in the ground or one of the latest and best above ground pools, one of the more important calculations you need to know for its care and maintenance is the volume of water it holds. The math for this is fairly easy to calculate, so we’ll show you how you can figure out the number of gallons of water your pool can hold.
The one key figure that you need to have is the cubic feet your pool happens to have. If your owner’s manual doesn’t have this figure listed in it, then you can figure it out on your own. You’ll just need to measure the length, width and the average depth of your pool to obtain the cubic feet. The equation requires you to multiply each one like this.
Length x Width x Average Depth = Cubic Feet
If you have a variable depth pool, it may be easier to measure each section of depth instead of the entire pool at once. In this instance, you’ll still use the above formula for each section. Then you’ll simply add the cubic feet numbers together once you’ve finished all measurements and this will give you the final number you need.
What is my swimming pool is circular? You can still quickly figure out the cubic feet of your pool, but the mathematical formula is a little more advanced. The first thing you’ll need to do is measure the entire distance across the pool. Divide that total distance in half, so if the pool was 90 inches across, half of that would be 45 inches. That’s called the “radius.”
Now you’ll need to multiply that number by itself – this is called “squaring” it. You’ll then need to determine the average depth of the pool. Then you can determine the cubic feet the circular pool contains with this formula.
Pi (3.14) x Radius Squared x Average Depth = Cubic Feet
Pi is used in the cubic feet formula for circular pools because it is a mathematical constant. It’s the ratio of a circle’s circumference to its diameter.
What if my pool has an irregular shape? This is primarily for in-ground pools. It is typically easier to break the pool down into areas that are easy to measure using the first formula. Then you simply make an adjustment to the calculation because of the shape. It looks something like this.
0.45 x (Shortest Width + Longest Width) x Length x Average Depth = Cubic Feet
Now here’s the really easy part about discovering the volume of water in a swimming pool. Once you know the cubic feet of a pool, you just multiply that number by 7.5. This is because there are always 7.5 gallons of water which fill a cubic foot.
Knowing this information allows you to get your pool chemistry right. So if you’re not sure about how many gallons your swimming pool can hold, use these formulas to your advantage and you’ll be able to figure it out in no time at all