Calculate your pool volume using a formula and simple math.

Determining volume for rectangular pools like the one to the right can be relatively simple. However, what happens when you have a lagoon style pool with a less “square” layout?

Use our pool volume guide to help determine an accurate volume for your pool.

Chemical Calculation

1. Take a water sample from the pool.

2. Add sodium bicarbonate (baking soda) to the pool. Add enough bicarb to make a measurable change (this will be about 2-4 pounds per 10,000 gallons). Make sure you weigh or measure the chemical and try to add exactly 2, 3 or 4 pounds. Make a note of how much chemical you added.

3. Wait long enough for the chemical to be completely dispersed and blended throughout the entire pool. (This will vary from minutes to even hours depending on method of addition and circulation.)

4. Take a second water sample from the pool.

5. Test the total alkalinity of the two samples. For sufficient accuracy, use a test method that is accurate to within 1 or 2 ppm.

For example; if your test kit uses 1 drop of titrant for each 10 ppm of total alkalinity, use a sample volume that is 10 times the sample size. Then each drop of reagent or titrant used is 1 ppm instead of 10 ppm.

7. Apply the following formula using the formula factor for sodium bicarbonate (The Formula Factor for sodium bicarb is 71,400).

(71,400) × (Amount of bicarb added to pool in lbs – 2, 3 or 4 lbs) / ppm change (From Test Step 5) = Pool Volume

For Example: You add 4 pounds of sodium bicarbonate to the pool. The starting total alkalinity was 110 ppm and the ending total alkalinity was 115 ppm.

(71,400 ) (4) / 115 – 100 = 19,040

Your calculated pool volume is; 19,040 Gallons

Dimension Measurement Calculation

Simple Pool Volume Guide for rectangular pools.

1. Measure the length, width and the depth (or average depth for pools with varying depths) of the pool and make note of these measurements. Multiplying these measurements will give you the cubic feet of the pool.

2. Multiply the cubic feet of the pool by the amount of water in a cubic feet.

Note: There are 7.5 gallons of water in a cubic foot.

3. Plug your measurements into the formula below to determine the volume of the pool.
(Length X Width X Depth or Average Depth) X 7.5 = Volume of Pool


Robert Lowry – Lowry School for Pool & Spa Chemistry – Pool Volume Calculator