Miles Per Gallon (MPG) Calculator
Work out your car's real fuel economy, your cost per mile and the total fuel cost of a trip — whether you know the miles and gallons from one trip, or want the accurate MPG measured between two full fill-ups. Everything runs privately in your browser.
What is MPG?
MPG, or miles per gallon, is the standard measure of fuel economy in the United States. It tells you how many miles a vehicle can travel on a single gallon of gasoline — so a car that gets 25 MPG can drive 25 miles for every gallon it burns. It is a simple, intuitive number: the higher the MPG, the more efficiently a vehicle converts fuel into distance, and the less money you spend. Because gas prices vary and your driving style changes from week to week, a calculator is the best way to get a number that reflects your car rather than a brochure estimate.
There are two common ways to compute MPG. The simpler way divides the miles you drove on a trip by the gallons you used. The more reliable way is the full-tank method: note the odometer at a full tank, drive and refill, then divide the miles covered by the gallons needed to top up — that smooths out tank-to-tank error for the most accurate figure. Both methods are covered here, and an optional gas price turns your MPG into a cost per mile and total trip cost.
How to use
- Choose a tab: Single trip uses miles driven and gallons used, Between fill-ups uses two odometer readings.
- Enter the miles driven (or your two odometer readings) and the gallons of gas used.
- Optionally add the gas price per gallon to see cost per mile and trip fuel cost.
- Click Calculate MPG to see your fuel economy and costs instantly.
Example
Enter 300 miles and 12 gallons on the Single trip tab for 25 MPG. Add a gas price of $3.50 and it returns $0.14 per mile and a $42.00 trip cost. Using Between fill-ups, odometer readings of 40,000 then 40,300 with 12 gallons give the same 25 MPG.
Common use cases
- Checking the real fuel economy of a new or used car before you buy.
- Budgeting the fuel cost of a road trip or daily commute.
- Comparing the efficiency of two vehicles or two driving styles.
- Tracking whether a tune-up or tire change actually improved your MPG.
Pro tips
- Measure MPG over two or three fill-ups, not one, for a more reliable figure.
- City stop-and-go driving uses more fuel than steady highway cruising.
- Under-inflated tires and excess weight can quietly cut several MPG.
- Use the cost per mile figure to compare driving against rideshare or transit.
FAQ
How do I calculate MPG?
Divide the miles you drove by the gallons of gas you used. For example, 300 miles on 12 gallons is 300 ÷ 12 = 25 MPG.
How do I calculate MPG between two fill-ups?
Subtract the previous odometer reading from the current one to find the miles driven, then divide by the gallons it took to fill the tank. That gives your real-world MPG.
What is a good MPG?
For a typical US car, 25 to 35 MPG is considered good, while 40+ MPG is excellent for a compact or hybrid. SUVs and trucks usually fall between 18 and 25 MPG.
How do I calculate cost per mile for fuel?
Divide the price per gallon by your MPG. If gas costs $3.50 a gallon and you get 25 MPG, your fuel cost per mile is $3.50 ÷ 25 = $0.14, or 14 cents.
What is the difference between MPG and L/100km?
MPG is miles per gallon, a higher-is-better measure. L/100km is a lower-is-better measure. To convert US MPG to L/100km, divide 235.2 by the MPG value.
Is a higher MPG always better?
Yes. A higher MPG means you travel farther per gallon, so you spend less fuel and less money per mile. Hybrids and EVs with high MPGe reflect this.
How can I improve my fuel efficiency?
Keep tires inflated, drive at steady speeds, avoid hard acceleration, remove excess weight, and keep up with scheduled maintenance to raise MPG.
How much does it cost to drive 100 miles?
Multiply your cost per mile by 100. At $0.14 per mile, driving 100 miles costs about $14 in fuel, assuming $3.50 gas and 25 MPG.
How do I get the most accurate MPG reading?
Use the full-tank method: fill up, reset the trip odometer, drive normally, then refill and divide the miles by the gallons added across two fill-ups.
Is this MPG calculator free and private?
Yes. It is completely free, runs entirely in your browser, and nothing you enter is uploaded.
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