Calculating Gas Mileage in Miles per Gallon (MPG)

Are you convinced that the EPA window sticker lied to you about your car's estimated mileage? Well, they might be wrong (it wouldn't be the first time); then again, you may not be calculating yours correctly. Don't panic: it's totally easy to do! All you'll need are a pencil and paper, or a calculator if you've forgotten how to do long division by hand.

Step 1: Fill your gas tank. Let the pump run until it shuts off by itself. Don't top off the tank, this adds to air pollution and wastes a little gas.

Step 2: If you have a trip odometer, zero it before you leave the pump. If you don't have one, record the odometer reading - I often write the number on the receipt.

Step 3: Drive until you need to refuel.

Step 4: Fill the tank again; remember to not overfill. Record the number of gallons from the pump readout; the number usually appears on the receipt as well (example: 12.45 gallons). This is the NUMBER OF GALLONS CONSUMED

Step 5: If you have a trip odometer, record the miles driven since the last fillup (writing it on the receipt works fine). If you don't have a trip odometer, record the odometer reading just as in step 2, and subtract the mileage at your last fillup from this new number (example: 109234 - 108891 = 343). This is the NUMBER OF MILES DRIVEN.

Step 6: To calculate gas mileage, the formula (eeek!!!) is

NUMBER OF MILES DRIVEN

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NUMBER OF GALLONS CONSUMED

You can do this with a calculator, by long division on paper, or in your head...

In our example, the gas mileage is

343 / 12.45  =  27.55 MPG

And that's all there is to it!