How To Calculate Pool Gallons

How To Calculate Pool Gallons

Calculating the volume of water in your pool is essential for maintaining proper water chemistry, selecting the right pool equipment, and ensuring overall pool functionality. Whether you have a rectangular, round, or irregular-shaped pool, determining the number of gallons your pool holds is crucial. Here is a step-by-step guide on how to calculate pool gallons based on different pool shapes:

Rectangular Pool Volume

For a rectangular pool with a constant depth, you can use the formula: Length x Width x Depth x 7.5 = Volume (in gallons). If your pool is 32 feet long, 16 feet wide, and 4 feet deep, the calculation would be: 32 x 16 x 4 x 7.5 = 15,360 gallons.

For rectangular pools with variable depths, where there is a gradual slope, calculate the average depth first by adding the shallow end depth to the deep end depth and dividing by 2. Then, multiply the length, width, average depth, and 7.5 to find the volume in gallons.

Round or Circular Pool Volume

For round pools, use the formula: 3.14 x Radius^2 x Depth x 7.5 = Volume (in gallons). If your pool has a diameter of 18 feet, a radius of 9 feet, and a depth of 4 feet, the calculation would be: 3.14 x (9 x 9) x 4 x 7.5 = 7630.2 gallons.

Irregular-Shaped Pool Volume

Irregular-shaped pools like ovals or kidney shapes require breaking down the pool into smaller, regular shapes for calculation. Measure each part, calculate the volume for each section using the respective formulas, and then add all the volumes together for the total pool volume.

When To Ask a Professional

If you have a pool with a unique shape or if you want precise measurements, consider consulting a pool professional to accurately measure and calculate the pool volume. This is crucial for chemical dosing, equipment installation, and overall pool maintenance.


1. How do I calculate pool volume for irregular-shaped pools?

For irregular-shaped pools, break down the pool into smaller regular shapes, calculate the volume for each section, and then sum up the volumes for the total pool volume.

2. When is the best time to add pool chemicals?

It is recommended to add chemicals like acid and shock at night and let the pool filter run for at least 8 hours before swimming.

3. How do I determine the right pump size for my pool?

Calculate the pool volume by multiplying the length, width, and depth, then multiply by 7.5 to get the volume in gallons. Choose a pump based on the total volume of the pool.

4. Can I swim immediately after adding pool chemicals?

Avoid swimming immediately after adding chemicals like acid or shock. Wait for a minimum of 8 hours to ensure proper chemical distribution in the pool water.

5. Why is it important to know the pool volume?

Knowing the pool volume is crucial for accurate chemical dosing, equipment sizing, and overall pool maintenance. It ensures a healthy and balanced pool environment.

6. How can I calculate pool volume for a round pool?

For round pools, use the formula: 3.14 x Radius^2 x Depth x 7.5 = Volume (in gallons). Measure the diameter, calculate the radius, and multiply by the depth to find the volume.

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