How to Calculate Gallons in a Pool

Calculating the volume of a swimming pool in gallons is an important task, since most pool treatment chemicals or cleaners require an estimate of size in gallons in order to provide an effective treatment dose, according to Conley Company, a wholesale supplier of pool equipment. Although figuring the gallons in a pool might seem like a complicated task, simple measurements and formulas make it easy.

Instructions

Calculate pool volume in gallons

1. Determine the shape of your pool. The shape will determine the measurements you make and the formula you will apply. Pools shapes fall into the following categories.

   - Rectangular
   - Round
   - Elliptical
   - Oval--the middle is rectangular and the ends are semicircular
   - Bean or kidney shaped
   - Free-form

2. Take measurements of the surface of your pool in feet. The measurements you make vary by the shape of your pool.

   For a rectangular pool, measure the length and width.

   For a round pool, measure the diameter.

   For an elliptical pool, measure the length and width (long and short diameters).

   For an oval pool, measure the overall length and the width.

   For a bean-shaped pool, measure the length. Find the average of the width of one end at its broadest point and the width of the other end at its broadest point.

   For a free-form shaped pool, measure the length. Take several different measurements of the width at different point and use those measurements to find the average width.

3. Calculate the average depth of the pool in feet. Average depth helps simplify the process of finding total volume of a pool by accounting for the slant at the bottom of most swimming pools, according to Backyard City Pools. Measure the depth of the shallow end and the depth of the deep end in feet; add these two measurements together and divide by two. The result is the average depth.

4. Find the capacity of the pool in gallons.

   For a rectangular pool, multiply the length by the width, then multiply by the average depth. Multiply the product by 7.5 to find the capacity in gallons.

   For a round pool, square the diameter and multiply by the average depth. Multiply the product by 5.9 to find the capacity in gallons.

   For an elliptical pool, multiply the length by the width, then multiply by the average depth. Multiply the product by 5.9 to find the capacity in gallons.

   For an oval pool, multiply the overall length by the width, then multiply by the average depth. Multiply the product by 6.7 to find the capacity in gallons.

   For a bean-shaped pool, multiply the length by the average width, then multiply by the average depth. Multiply the product by 7.0 to find the capacity in gallons.

   For a free-form pool, multiply the length by the average width, then multiply by the average depth. Multiply the product by 7.5 to find the capacity in gallons.

Tips & Warnings

• While the gallons calculated for each shape of pool are all approximate, the calculations are most accurate for rectangular, round, and elliptical pools. For a pool with a free-form shape, it's advisable to consult your pool builder or a specialist for a more accurate calculation of volume.

References

• Conley: Pool Size Calculator
• Backyard City Pools: How to Calculate Your Swimming Pool Water Volume
• Pool Info: Calculating the Volume (Gallonage) of Your Swimming Pool