Knowing this, you can return to the formula:ģ.14 x radius squared x average depth x 7.5 = volume (in gallons)ģ.14 x 25 ft x 3 ft x 7.5 = 1766.25 gallons Squared (multiplied by itself) means 5 feet times 5 feet equals 25 square feet. Use the hot tub to calculate the volume of a round container. For example, if you measure the radius as 5 feet, multiply 5 feet by 5 feet to arrive at 25 feet. Squared means multiplied by itself, so multiply the radius by itself. The radius is one-half the diameter, so measure the distance across the broadest part of the circle and divide it in half to arrive at the radius. The number 3.14, refers to pi, which is a mathematical constant. The formula: 3.14 x radius squared x average depth x 7.5 = volume (in gallons) In the example, that was 4 feet.Ģ5.75 ft x 10 ft x 6 ft x 7.5 = 11,587.5 gallons Then, of course, you would use the actual depth (or average depth) measurement. There might be a time when you want to know the potential volume, if filled to the brim. This could mean serious errors when adding chemicals for example, which are administered based on the volume of water in question. Using 4 feet in this calculation will result in a volume 33 percent greater than the actual amount of water. For example, the hot tub depicted in Figure 2 is 4 feet deep, but the water is only filled to about 3 feet. Make sure to use the actual water depth in your calculations, not the depth of the container. Calculate the volume of the shallow section and add that to the volume you calculate for the deeper section. Measure the length, width, and average depth of the shallow section, then take the same measurements for the deeper section. In such a case, you might want to treat the pool as two parts. If most of the pool is only 3 or 4 feet and then a small area drops off suddenly to 10 feet, you will have a different average depth. If the shallow end is 3 feet and the deep end is 9 feet, and assuming the slope of the pool bottom is gradual and even, then the average depth is 6 feet.Īverage depth = ( Depth at the shallow end + Depth at the deep end ) / 2 Therefore, multiply the number of inches in your measurements by 0.0833 to get the appropriate percentage of one foot.Įxample: 25 ft, 9 in. Measure the length, width, and average depth of the pool, rounding each measurement off to the nearest foot or percentage of one foot. Since there are 7.5 gallons in each cubic foot, multiply the cubic feet of the pool by 7.5 to arrive at the volume of the pool (expressed in gallons). Multiplying that by the average depth gives the volume in cubic feet. Length times width gives the surface area of the pool. Length x width x average depth x 7.5 = volume (in gallons) Variable Depth Pools: Square and Rectangular Guide to Cleaning Pool Filter Cartridges.

Round pool volume calculator