Welcome to our swimming pool math section. We feature calculators & apps for pool chemistry, water volume, surface area, and more.

swimming pool calculator apps

If the reasons are not obvious, here is why. You will need to know a few approximate details regarding your pool specifically. The reasons are for pool water treatment using chemicals, such as shocking the pool water. Without knowing how much water your pool holds you will not know how to determine the amount of chemicals to add to the pool.

You should keep notes on your swimming pool, namely the size and depth information at the least. If you do not already have notes saved about your pool, go and create a notebook dedicated to the it, this will come in handy more times than you think.

If you have these details, such as your pool water capacity and surface area it will be easy for you to DIY pool repairs or to compare estimates when looking to hire for these repairs.

Note: If you are the original owner of the pool you should have documents and drawings that include the pool measurements, in this case you can skip the measuring procedures, you should have what you need already.

Pool Surface Area

Swimming Pool Surface Area Calculator

Pool Capacity Calculator

Swimming Pool Capacity Calculator

Having concerns about these results? > Ask a pool pro!


how to measure a swimming pool for water volume calculation

Now that you have a means of keeping notes on your pool, let’s begin with “How to measure your pool for water calculations”.
Here are the tools you will need to get all the measurements:

  • A tape measure (that is at least 35ft long)
  • You might need a second person to help hold your tape measure

Now that we have the tools needed to measure the pool, let’s actually get those measurements, here is how you do it.

Rectangle & geometric pool shape measurements:

Note: Areas of the pool that are cut out from the main shape will need to be added in to the measurements. This can also be used for measuring square & rectangle spas.

  • Step 1 – Measure the total length of the pool from the inside wall to the adjacent inside wall. (from tile tot tile on opposite sides)
  • Step 2 – Measure the total width of the pool inside wall to inside wall.
  • Step 3 – Measure the depths. Get approximately above the deepest point. Use your tape measure from the bottom of the pool up to the water surface.
  • Step 4 – Record all of these measurements into your notes about the pool.
  • Step 5 – Use our pool volume calculators above with the numbers you have to get the total water volume capacity of your pool.

Ellipse, Oval, and Irregular Circular pool shape measurements:

  • Step 1 – Measure the total diameter of the spa and divide by 2 to get the radius.
  • Step 2 – Measure the depth by using the tape measure at the center of the spa bottom up to the water level. Typical spa depth is around 42 inches of water.
  • Step 3 – Record these numbers in the spa section of your notes.
  • Step 4 – Use our circular volume calculator above to get the approximate water capacity of the hot tub or spa.


Measuring a swimming pool surface area is like finding the area of a room, in terms of the flat surface – the pool “footprint” so to speak. This is a very useful measurement to know for pool owners, especially when it comes to things like pool pricing for repairs or remodeling.

In certain cases with pools having more complex designs, you may need to measure in sections and add the totals.


You will need to know how many gallons of water your pool holds to properly administer the chemicals and / or when you need to make special adjustments to the water when you experience an adverse pool water condition.

Volume is the amount of space taken up by a three-dimensional object, like a swimming pool. Volume often refers to liquid capacity, which is the amount of space taken up by a liquid to fill its container. This is an approximate calculation of the total amount of gallons of water the pool can hold, also known as pool capacity.


NoteInteresting finds when measuring pools: Often times we see that pool owners are surprised when they realize the pool is either less or more deep than what they were told. This is evident when accurately measuring the pool to double check what you were told by the pool builder or the home seller.