How to measure the fuel oil in a tank

Updated February 21, 2017

Knowing the amount of fuel in a tank is important for projecting how long it will last. Running out of fuel at a pivotal time can cause a major headache, or worse, create and unsafe situation. Calculating the amount of fuel in any tank is a simple task that should take no more than a few minutes.

Open the top of the tank and put a large measuring stick into the liquid until it hits the bottom of the tank.

Record the number of centimetres of liquid there are in the tank. This will be the depth from the end of the stick that is in the liquid to the line where the stick exits the liquid.

Measure the diameter of the cylindrical tank in centimetres. If you have a rectangular tank, measure the width and length.

Calculate the amount of liquid in the tank by multiplying pi times half of the diameter squared times height of the liquid. If you have a rectangular tank, multiply the length times width times height of the liquid.

Convert the calculation into litres by taking the answer from the step above and multiplying by 0.001.


If you would like to know the total capacity of your tank, repeat steps 3 through 5 but use the total height of the tank as your height measurement. If you don't have a measuring stick, you can make centimetre markers on a broom handle and use that.


Make sure the measuring stick is thoroughly cleaned before you put it in the fuel, otherwise you may contaminate it.

Things You'll Need

  • Measuring stick
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