- 1). Measure length and width of the pool, with the measuring tape. Record these measurements in inches for right now. For example if the pool is 5 feet and 6 inches by 7 feet, then the measurement should be 66 inches by 84 inches, respectively.
- 2). Multiply the width by two and the length by two. The example would be: (2 x 66) and (2 x 84).
- 3). Add the result of the width and the length together. For example, the formula should read: (2 x 66) + (2 x 84)= 300 inches. This is the perimeter of the pool.
- 4). Convert the perimeter to linear feet by dividing the answer by 12. The example is: (300/12) = 25 feet.
- 1). Measure the length and width of the pool, using the tape measure. Keep the measurements in inches for a more accurate result.
- 2). Multiply the length by the width. For example, a measurement for a pool of 66 inches by 84 inches would read: 66 x 84 = 5544 square inches.
- 3). Convert the answer to square feet by dividing the amount in square inches by 144. The above example will be: (5544/144) = 38.5 square feet.
- 1). Measure the length, width and average depth of the pool, in feet. The average depth is the depth of both the shallow and deep end added together then divided by 2. For a pool with a shallow end of 2 feet and a deep end of 10 feet, the average depth is: (2 + 10)/2 = 6.
- 2). Multiply the length, width and average depth together. A pool with measurements, in feet, of 10 x 12 x 6 would have a volume of 720 cubic feet.
- 3). Multiply the volume by a gallon multiplier -- 7.5 for a rectangle-shaped pool. This will give the approximate amount of gallons it takes to fill the pool. The above example will be: 720 x 7.5 = 5400 gallons.