MPG calculator
Miles per gallon from a fill-up.
Put this calculator on your site
Get it as a ready-made Gravity Forms template. Import it, match your colors, publish.
- Import-ready form file
- Step-by-step build guide
- Works with any theme
How it's calculated
Fill the tank, reset the trip odometer, drive, and fill it again: the miles on the trip counter divided by the gallons it took to refill is your real-world fuel economy. Price times gallons over miles gives the fuel cost of each mile. The metric conversions use 235.215 litres per 100 km for 1 MPG, and 1 MPG = 0.4251 km per litre (US gallons).
Why is my MPG lower than the sticker?
The EPA figures come from a lab cycle. Short trips with a cold engine, city stop-start, speeds over 70 mph, roof racks, under-inflated tyres and winter fuel all cost economy. Being 10–20% under the combined rating is normal.
How accurate is one fill-up?
Within a few percent if you fill to the first click both times at the same pump angle. Average three or four tanks for a figure you can trust; a single short tank can be off by 10% from where the pump cut off.
Are these US or UK gallons?
US gallons (3.785 litres). A UK gallon is 4.546 litres, so UK MPG figures are about 20% higher for the same car. The litres per 100 km result is the same either way once the gallons are entered correctly.
Results are estimates for informational purposes only and are not financial, medical or legal advice.