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Pool Calculator

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How does the pool volume calculator work?Formulas behind pool calculatorHow many gallons is my pool?Olympic swimming pool volumePool calculator and other related toolsFAQs

The pool calculator tells you how much water you will need to fill pools of various sizes and depths. 🏊 This is useful information that will help you to estimate better the cost of the water, as well as the amount of time you need to go from an empty pool to floating around with a cool drink in your hand. If you're wondering how many gallons your pool has, give this tool a try!

Please note that the pool volume calculator assumes that the depth of the pool changes evenly and gradually from one end to the other, as is generally the case. If this does not apply to your pool size, figures computed by the pool calculator are still in the right ballpark.

How does the pool volume calculator work?

Image of a pool, the depth changing linearly.

Finding the volume of a pool is a simple matter of getting the area of the surface of the pool and then multiplying that by the average depth.

  • Start by entering the pool size (length and width).
  • Then add its depth at the two endpoints.
  • If there is both a shallow and a deep end, enter the shallow depth in the first field and the deepest point in the second. Otherwise, enter two identical values.
  • If the depth of your pool changes drastically instead of gradually, you may want to consider dividing it in half, with a separate pool calculator measurement for each part (as in the image on the right).
Pool with two parts of different depth.

You could go one step further and, knowing the density of water (which is approximately 1 kilogram per liter), work out how much the water in such a pool would weigh.

Formulas behind pool calculator

So you no longer need to worry "how many gallons is my pool?," simply apply one of the formulas:

  1. Rectangular/square pool
V=l×w×d1+d22V = l \times w\times \frac{d_1 + d_2}{2}


  • VV – Pool volume;
  • ll – Length of the pool;
  • ww – Width of the pool;
  • d1d_1 – Depth at one end of the pool; and
  • d2d_2 – Depth at another end of the pool.

The first two agents are, of course, the formula for the area of the rectangle.

  1. Oval/circle pool
V=π×l×w4×d1+d22V = \frac{\pi\times l\times w}{4} \times \frac{d_1 + d_2}{2}

The first part of the equation comes from a standard area of an ellipsis formula: A=π×a×b\small A = \pi \times a\times b, where a\small a, b\small b are the distances between the center and the ellipse's vertex, lying on the horizontal and vertical axes. In our case, we have the length and width values that are the doubled distances where a\small a and where b\small b, so in the final formula, we need to divide the surface area of an oval by 4.

Image of a pool, the depth changing linearly.

You are wondering why we average the depths d1+d22\small \frac{d_1 + d_2}{2}? Have a look at the pictures:

  1. Here you have the standard rectangular pool.
Right trapezoidal side of the pool.
  1. Let's take the right trapezoidal side of the pool. "Cut" the triangle, with one apex in the midpoint of the side, as in the picture.

  2. Flip and move it to the other side to form a rectangle. The edge of the new shape is the average of two sides, so d1+d22\small \frac{d_1 + d_2}{2}.

Right trapezoidal side changed into rectangle.

The area of such a rectangle is then l×d1+d22l\times \frac{d_1 + d_2}{2}. Multiply it by the third dimension - the width - and you'll get the final formula for rectangular pool volume:

V=l×w×d1+d22V = l\times w\times \frac{d_1 + d_2}{2}

How many gallons is my pool?

Let's calculate it with this pool volume calculator!

  1. Choose the shape of your pool. You can select between two types - rectangular/square pool or oval/circle one. Our example is with a standard rectangular pool, so leave the default value.

  2. Enter the dimensions of the swimming pool. Let's say that the pool is 12 ft wide and 50 ft long. Depth is gradually changing from 4 to 6 feet.

  3. The pool calculator shows the volume of water needed to fill up the pool. In our case, it's 22,441.57 US gallons.

Our tool is sometimes called the pool size calculator or pool gallon calculator because it works with any unit, not just with metric units. If we didn't auto-detect your preferred units, click on the unit to select from a range of available units.

If your pool doesn't vary in depth but is some kind of a fancy shape like a bow front or cylinder, check out this aquarium calculator - it has some nice options for different 3D shapes. If the pool of your dreams comes in some custom or eccentric shape, check out the manufacturer's website.

  1. If you know the price of water in your area, you can calculate the cost of filling up your pool. Click on the Water cost heading, and an additional part will appear. The pool gallon calculator takes the result of the previous section and multiplies it by the applicable rates of your local water supply. And that's all you need to do to find out how much beating the heat will cost!

    Let's take the average cost of water in the US, which is $1.50 per 1000 gallons. For our exemplary pool, the cost of water is $33.66. Not so bad, huh?

This calculator finds the total volume of your pool - in reality, you never fill the pool all the way to the brim.

Olympic swimming pool volume

To calculate the Olympic swimming pool volume, you need to know its dimensions. The length of the pool is 50 m, width 25 m, and the depth varies: 2.0 m is the minimum, but 3.0 m is the recommended depth.

Olympic-size swimming pool contains 2,500,000 L of water, assuming a nominal depth of 2 m. It's around 550,000 imp gal and 660,000 US gal. Try to calculate the Olympic swimming pool volume for a recommended depth of 3 meters - or use the pool calculator to get the answer in the blink of an eye.

Have you ever wondered how many tea- or tablespoons of water can fit into the Olympic swimming pool? We haven't, either. But now you can check it! Awesome, isn't it?


How to calculate the water I need for my pool?

To find the water you need for your pool:

  1. Measure the length and width of your pool.
  2. Measure the depth of the pool from where you'd like the waterline to be. If your pool's depth varies, take the average depth of both ends.
  3. Ensure length, width, and depth are all in the same units.
  4. Multiply the three measurements together to get your pool volume.

How much chlorine do I need for my pool?

To find the amount of chlorine your pool needs:

  1. Determine the volume of your pool.
  2. Refer to the chlorine manufacturer and find the ratio of water/chlorine you need to use. You can also consider using 52-104 oz of liquid chlorine (1.5 - 3.1 liters ) per 10,000 gallons of water (38 cubic meters). The equivalent ratio is 8.15 liters per 100 cubic meters.
  3. Multiply your pool volume by the chosen ratio, keeping both units of volume the same, and you will get your chlorine requirement.

How many gallons do I need for my pool?

To find the amount of gallons you need to fill your pool:

  1. Measure the length and width of your pool in feet. You also need to know the average depth in feet.
  2. Determine the volume by multiplying all three measurements together. The result will be in cubic feet.
  3. Multiply the result by 7.5 to convert the volume into US gallons.

How much it cost to fill my pool?

To find the cost to fill you pool:

  1. Measure the length, width, and average depth of your pool.
  2. Multiply all three values together to find the volume.
  3. Find out the cost of water per unit volume from with your local water provider.
  4. Multiply the total water requirement per unit price to get the total cost.



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