Pool Calculator: how to measure your swimming pool
Figuring out exactly how much water is in your pool is of critical importance – and not just so that you know how long you have to leave the hose running to fill it up, either!
No, the water volume that you have in your swimming pool is going to dictate exactly how much chlorine and other chemicals you are putting into your pool to keep it crystal-clear and pristine all summer long without causing any health risks along the way.
Unfortunately, a lot of pool owners have little to no idea of how much water exists in their pool and just kind of “eyeball” these measurements. This approach inevitably leads to swimmers dealing with irritated skin, burning eyes, and all kinds of other issues or a pool that just won’t clear but is instead murky and cloudy pretty much all year round.
Thankfully though, it’s pretty simple and straightforward to calculate just how much water your swimming pool holds using the inside information we highlight below.
There are plenty of tools online to help you knock this out of the park as well, but we go through the step-by-step process you’ll want to follow in this quick guide so that you know exactly how to calculate this figure moving forward.
Let’s dig right in!
Benefits of Understanding Exactly How Much Water Your Pool Holds
Right out of the gate, it’s important to highlight a couple of the big benefits you get from figuring out exactly how much water your pool is going to hold.
To begin with, knowing exactly how much water your swimming pool can contain is going to make it a lot easier to both fill and empty your swimming pool whenever necessary.
Ordering a pump tank with just the right amount of water to fill your swimming pool makes quick work of the process, rather than letting a garden hose pump for hours and hours and hours (days, usually) to get your water level exactly.
Of course, you have to know exactly how much water you are ordering from a pump tank service ahead of time – which is where calculating this figure comes into play.
Secondly (like we highlighted above) figuring out exactly how much water your swimming pool holds is mission-critical for measuring out the right amount of chemicals to add at any one particular point in time.
Every swimming pool (aside from those tiny kiddie swimming pools) will need a bit of maintenance now and then.
At the same time, the chemicals that you’ll use to clean and maintain your pool – chlorine, pH increasers, chemical shocks, etc. – can all be rendered completely ineffective if you aren’t using enough of these chemicals, but can also be incredibly dangerous if you are using too much.
By knowing exactly how much water you have in your pool and how much water needs to be treated you’ll be able to add just the right amount on a consistent basis. This guarantees that your water stays completely healthy for swimming and crystal-clear all season long without risking irritated skin, burning eyes, or ammonia and algae issues.
Lastly, it’s not a bad idea to know exactly how much water you have in your swimming pool if you need to heat it on a regular basis.
This calculation will let you know how much water needs to be on a continuous basis, the size of the heating system will need to use, and the expense that you are going to be looking at running this heating system all the time.
As you can see, there are a lot of moving pieces regarding your swimming pool that is almost entirely dependent on you know how to calculate pool water volume accurately.
Quick Pool Volume Calculation Formulas
As we highlighted above, there are a couple of charts you can find online to help you calculate at least a ballpark figure of the amount of water you have in your swimming pool – but if you really want a highly accurate figure we are going to lay out the math you’ll want to know below.
To begin with, you are going to need to understand a handful of key equation elements and measurements that will be necessary for this calculation.
You’ll need to know the following about your swimming pool:
- Height Volume
You’ll also need to use these figures to calculate the overall cubic volume of your swimming pool – and that means that you need to know the depth of your pool and the surface area to really zero inaccurately.
Remember that a single cubic foot of water is made up of 7.5 gallons. As long as you can determine the cubic foot measurement of your pool you’ll be able to then multiply that number by 7.5 and you’ll hit your volume figures.
Working with a Square or Rectangular Pool?
If you have a square or rectangle early shaped swimming pool with a constant depth – no shallow end or deep end, just one flat bottom across the board – the process is pretty simple and straightforward.
Just measure the length of your swimming pool and the width of your swimming pool to get the overall surface area figure. Multiply that number by the depth of your swimming pool to get its cubic feet measurement, and then multiply that final number by 7.5.
Let’s say you have a 32-foot long swimming pool that is 16 feet wide with a depth of 4 feet consistently. Running the calculation we highlighted above you to discover that your pool holds 15,360 gallons of water.
If you have a variable depth pool (a pool with a deep end and a shallow end) the calculations get a little bit more complex but still pretty easy to knock right out of the park.
For starters, you’ll want to figure out the “average depth” of your swimming pool. Simply add up the shallow end depth to the deep end depth numbers and then divide that figure by two and you’ll have hit your average depth number.
Run through the same equation that we highlighted above (length x width x average depth x 7.5) and you’ll get to your volume number.
That same 32 ft long and 16 ft wide swimming pool with an average depth of 6 feet would take 23,040 gallons of water to fill.
Circular Pool Volumes
Circular shaped swimming pools are pretty easy to calculate. After all, all you have to do is multiply the number pi (3.14 for these purposes) by the radius squared – then multiply that number by the depth and the 7.5-gallon figure we highlighted earlier.
You’ll first have to start by measuring out the radius of your swimming pool. This means running a tape measure across the diameter of the pool, measuring it at its widest point. If your swimming pool is perfectly circular you’ll be able to use that number for the length of your swimming pool as well, though oblong-shaped swimming pools will obviously have a different number you need to adjust for.
After you have your diameter figures you’ll want to divide that number by two to get the radius.
Let’s just say for the sake of this example that you have a swimming pool that measures in at 24 feet at its widest point, the diameter. You’d divide that number by two, ending up with 12.
You then multiply that number by itself to get the radius squared, arriving at 144 feet.
Lastly, you’ll want to calculate the overall depth of your swimming pool (the constant depth or the average depth) – and let’s say for this example that you have a 4-foot deep swimming pool.
The final equation would look something like this:
3.14 x 144 x 4 x 7.5, which would result in a grand total volume figure of 13,565 gallons (rounding up).
At the end of the day, figuring out the total volume for your swimming pool is nowhere near as challenging as it might seem at first.
All you need is a handful of numbers that you can measure out yourself in about 15 minutes, quickly calculating exactly how much water your swimming pool can hold in total.
Now that you have the numbers in hand it’s a good time to analyze exactly how much chlorine, pH balancer, shock, and other chemicals that you have been putting into your pool just to see whether or not you are as dialed in as you had hoped you were.
The odds are pretty good that you’ll be close to where you want to be (especially if you’ve been following the manufacturer’s directions to the letter), but now is the perfect time to really zero in and hit those numbers perfectly going forward.
Your pool will become a whole lot easier to clean, maintain, and keep healthy all season long – and you’ll be able to get a lot more enjoyment out of it as well!