How-To: Know the Size of Your Swimming Pool

To maintain the health of your pool, there are two main areas to be considered:

• Chemical
• Mechanical

For the chemical part, you always need to estimate the size of pool first.  For example, if you need to add chlorine shock,  Leslie's Swimming Pool Supplies always ask your pool size in gallons before they decide how much chlorine powder you need for your pool.

If your pool has regular shapes such as rectangles or circles, it's relatively easy to come up the pool size.  For example, for a rectangular pool, its size can be estimated by:

Average depth * width * length

If you measure your three dimension in feet, you will come up total cubic feet of your pool size.

Converting Cubic Feet to Gallons

To convert cubic feet to gallons, you can use the following formula:

1 ft³ * 7.48 gallon/ft³ = 7.48 gallons

To simplify, you may use 7.5 instead of 7.48 in you calculation.  If you have an irregular shape, say, kidney shape as shown below, it takes a bit more effort.

Kidney or Irregular Shapes

There are different methods used to calculate the capacity of irregular shapes. First, you can imagine the pool as a combination of smaller, regular shapes. Measure these various areas and use the calculations described in [2] for each square or rectangular area and for each circular area. Add these volumes together to determine the total capacity.

Here we will introduce you another method.

Volume in gallons = (Estimated surface area * Average Depth) * 7.5 

where

Average surface area = (A+B) * C * 0.45

The total of measurement A plus measurement B multiplied by 0.45 multiplied by the length (i.e., C) gives you the surface area of the kidney shape.

References

1. How to Calculate Swimming Pool Volume in Gallons 
2. Pool Volume Calculator