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How to Calculate Dimensions With Gallons and Depths

The United States customary system employs gallon units to measure volume. The depth is measured in linear units such as inches or centimeters. For instance, you need to compute the dimensions of a fish tank if its depth is known and the volume is given in gallons. To make the required computation, you first need to convert gallons to cubic units -- for example, inches.

Things You'll Need

Calculator

Instructions

- 1
  Multiply the volume in gallons by 231 to convert it to cubic inches. For example, the volume of 20 gallons corresponds to 20 x 231, or 4,620 cubic inches.
- 2
  Convert the depth to inches. For example, if the depth is 70 centimeters, divide it by 2,54: 70/2.54 = 27.56 inches.
- 3
  Divide the volume by the depth to calculate the dimension product (area). In this example, the area is 4,620 / 27.56, or 167.6 square inches.
- 4
  Divide the area by one of the dimensions, such as a length, to calculate the other. In this example, if the length is 10 inches then the width is 167.6 / 10, or 16.76 inches.

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