Calculate Your Pool Capacity

When balancing your pool water it is important to know how many gallons of water you're treating. For example, if your alkalinity is at 20ppm and you need to jump it up 100ppm to get to 120ppm, then you'll need to know how many gallons of pool water you're dealing with so that you can calculate how much sodium bicarbonate to add. Here are the formulas for calculating your swimming pools capacity.

Square or Rectangular Pools

Length x width x average depth x 7.5 = valume in gallons

First we need to establish the surface area of the pool (L x W). Then we multiply that number by the average depth to get volume in cubic feet. To calculate average depth add all depths together and divide by the number of depths, for example 4 feet 5 feet 5 feet and 6 feet = 20 feet, now divide that by 4, because there's 4 depth factors, and our average depth is 5 feet. Because 7.5 gallons fits in a cubic foot, you multiply cubic feet by 7.5 gallons to arrive at your pool capacity.

Circular

3.14 x radius squared x average depth x 7.5 = volume in gallons

3.14 is the mathmatical constant. To calculate your pools radius, measure the pool across the broadest section, then take that number and divide it in half. For example if the pool is 10' across the broadest section, your radius is 5. squared means multiplied by itself, so 5 x 5 = 25 radius squared.

Kidney or Irregular

An irregulare shape pool looks like a rectangular pool but with rounded corners. For these pools you can measure the center rectangle and calculate per the formula above, then make a second calculation for the rounded ends using the circular formula, then add the two calculations together.

Kidney shapes will typically have a small rounded end and a larger rounded end. For these pools lets measure the width across each end, we will call these measurments A and B. Here's what the formula looks like.

0.45 x (A+B) x length x average depth x 7.5 = volume in gallons