How to Calculate Gallons of Oil in Tank

Written by raul avenir
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How to Calculate Gallons of Oil in Tank
Oil tanks and containers are rated by their volume capacity in gallons. (Oil Drums image by Yali Shi from

Oil is a very important commodity that you use daily. It is stored in various types and sizes of oil tanks to maintain its stock. It is considered to be a fast-moving commodity, and oil tanks that store oil are typically rated by the number of gallons that they can hold. Knowing the gallon capacity of an oil tank allows you to compute the number of days its supply will last. Learn how to estimate the volume of an oil tank and avoid a possible oil shortage.

Skill level:

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Things you need

  • Calculator
  • Measuring tape

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  1. 1

    Measure the dimensions of the oil tank. Measure its length, width and height if the tank is square or rectangular shaped. Measure its height and radius (distance from the centre to the side) if the tank is cylindrical in shape. Jot the numbers down on a piece of paper.

  2. 2

    Use inches and feet as your unit of measurement, and convert all measurements into decimal numbers. Divide any figure in inches by 12 (using your calculator) to get its decimal equivalent and add the resulting figure to the number of feet to get the final measurement. For example, in a measurement of 7 feet 3 inches, you need to convert 3 inches to its decimal equivalent by dividing it by 12 to come up with .25. Add .25 to 7 feet to give you a decimal measurement of 7.25 feet.

  3. 3

    Calculate the volume of a square or rectangular shaped tank in cubic feet. Multiply the length by the width, and multiply the resulting figure by the height (length x width x height) to arrive at its volume in cubic feet. For example, 7.25 feet (length) multiplied by 5 feet (width), and multiplied by 10.5 feet (height) will result to a volume of 380.62 cubic feet.

  4. 4

    Calculate the volume of a cylindrical tank in cubic feet. To get the volume of the cylinder, multiply the radius by itself, multiply the resulting figure by 3.142, and multiply the resulting figure by the height of the cylinder. For example, to get the volume in cubic feet of a cylinder having a radius of 3.5 feet and a height of 10 feet, multiply 3.5 (radius) by itself to get 12.25, multiply 12.25 by 3.142 to get 38.489, and then multiply 38.489 by 10 (height) to get a final answer of 384.895 cubic feet.

  5. 5

    Multiply the number of cubic feet by 7.48 to arrive at the number of gallons. For example, the volume in cubic feet of the rectangular tank in step 3 would be calculated by multiplying 380.62 by 7.48 to give you a final volume in gallons of 2847.03 gallons. The volume of the cylindrical tank in step 4 would be calculated by multiplying 384.895 by 7.48 to give you a final answer of 2879.01 gallons of oil.

Tips and warnings

  • When measuring oil tanks, always measure from the inside of the container. Do not include the thickness of the container walls in your measurement to get an accurate measurement.

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