Global Fuel CalculatorMPG Calculator — Miles Per Gallon, US and Imperial
This MPG calculator (a straightforward calculator for miles per gallon) works out MPG from a trip odometer reading and a fill-up, in both US and imperial gallons — the two are not interchangeable, and treating them as if they were is the single most common fuel-economy mistake. The result also includes cost per mile and the L/100km equivalent for comparing against a European or Canadian specification.
MPG works the same way whether the vehicle is a compact car, a truck, or you are averaging several tanks together for a combined figure. What changes between vehicles is only the number, not the method: miles driven divided by gallons used, converted at the end into whichever gallon you actually mean.
Work out your numbers
What changes your MPG
The sticker figure is a lab result. On the road, aggressive acceleration and hard braking, high cruising speed, cold weather (the engine takes longer to reach operating temperature), air conditioning, a roof rack, a trailer and extra weight all push consumption up. Four-wheel drive usually costs a little more fuel than two-wheel drive, and a bigger engine generally drinks more than a smaller one, though the technology matters as much as the size.
For an average MPG rather than a single-tank figure, add up the miles and the gallons across several fill-ups and divide total miles by total gallons. Do not average the individual MPG numbers, because a short tank would skew the result. Combined MPG blends city and highway the same way. And for a rough range, multiply your MPG by your tank capacity: 30 MPG on a 12-gallon tank is about 360 miles.
Common questions
How do I calculate my MPG?
Fill the tank, reset the trip odometer, drive until you need fuel again, then fill to the same cut-off. Divide the miles shown by the gallons it took to refill. 312 miles on 11.4 gallons works out to about 27.4 MPG.
What is a good MPG, and is 30 MPG good?
For a typical petrol car, 30 MPG is good: slightly better than average, and equal to 7.84 L/100km. For a small hatchback it is merely fair, and for a pickup it would be excellent. Remember that 30 UK MPG is only about 25 US MPG. Our guide to what counts as a good MPG goes through typical figures by vehicle type.
How do I calculate fuel cost from MPG?
Divide the trip distance by your MPG to get gallons needed, then multiply by the price per gallon. This calculator does that step automatically once you enter distance, MPG (or the fuel and distance used to derive it) and price.
How do I calculate the fuel cost for a trip using MPG?
Enter your established MPG, the current price per gallon, and your trip distance in the optional field. The calculator returns the gallons the trip will use and the total dollar cost, based on your own measured fuel economy rather than an assumed average.
What is a combined MPG figure?
It is a single number that blends city and highway driving, usually weighted toward how most owners actually drive rather than a straight average of the two. If you average several of your own tanks that mix commuting and longer drives, you are effectively producing your own combined figure.
How do I convert MPG to L/100km?
For US gallons, divide 235.21 by the MPG figure. For imperial gallons, divide 282.5 by it. This calculator shows the L/100km equivalent automatically next to your MPG result, so no manual conversion is needed.