How to Calculate the Volume of a Partially Full Tank

Many tanks have a label that states the amount of water that they hold, also known as volume. However, there are many situations where your tank is not filled up to the maximum capacity. It is not difficult to calculate the volume of a partially filled tank if you use the correct mathematical equations. The two most common tank shapes are rectangular and cylindrical.

Things You'll Need

  • Tape measure (that uses inches)
  • Calculator
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Instructions

  1. Square or Rectangular Tank

    • 1

      Measure the width and length of your tank in inches with the tape measure. Measure the height from lowest point of the water to the surface of the water in inches.

    • 2

      Multiply the width by the height by the length using your calculator. This number is the volume of the water in your tank in cubic inches.

    • 3

      Use your calculator to multiply the volume in cubic inches by .00433 to get the volume in gallons.

    • 4

      Multiply your volume in gallons by 16 if you wish to calculate the volume in cups.

    Cylindrical Tank

    • 5

      Make sure that your tank is standing so that one of the circular ends is flat on the ground. Measure the height of the tank from the bottom to the line of the substance inside, in inches. This is the height.

    • 6

      Measure the radius of one of the circular ends. The radius is the measurement from the point in the exact middle of the circle to any edge.

    • 7

      Multiply the radius by itself. For example: if the radius is 3 inches, multiply it by 3 to get 9 inches. Find the area of the circle in inches squared by multiplying this number by 3.14.

    • 8

      Multiply the area of the circle by the height of the cylinder to get the volume of the filled part of your tank in inches cubed.

    • 9

      Use your calculator to multiply the volume in cubic inches by .00433 to get the volume in gallons.