How to Calculate Sq. Foot to Gallons
- 1). Calculate the square footage of the bottom of the tank by multiplying the length times the width. To get the volume of the tank in cubic feet, multiply the square footage of the bottom of the tank by the depth of the tank.
- 2). Multiply the number of cubic feet by 7.4805194805 to obtain the precise number of gallons the tank will hold. You can approximate the number of gallons by multiplying the number of cubic feet by 7.5.
- 3). Measure the length, width and depth of a smaller tank in inches. Using your calculator, multiply the length times the width, and then multiply the result by the depth to obtain the number of cubic inches in the tank. Divide this sum by 231 to get the number of gallons the tank will hold.
- 4). Measure the length, width and depth in feet to determine the number of gallons in a fishpond or pool. If the pond or pool is an irregular shape, you will have to estimate. Using a calculator, multiply the length times the width, and then multiply the result by the depth to obtain the volume in cubic feet. Multiply that number by 7.4805194805 to obtain the number of gallons that the pond or pool will hold.
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