MPG calculator.

To find your MPG (miles per gallon), divide the miles driven by the gallons of gas you added. Driving 360 miles and filling up with 12 gallons is 30 mpg. At $3.50 a gallon, that is 11.7 cents per mile. A 300-mile trip at 28 mpg uses 10.71 gallons and costs $36.96 with gas at $3.45.

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Your car's miles per gallon

Tank-to-tank method: miles driven between two fill-ups and the gallons it took to refill.

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Fuel economycalterix
30 mpg
3.33 gallons per 100 miles and a fuel cost of 11.7 cents per mile
An estimate from the numbers you enter. Real fuel use depends on the vehicle, traffic, load, and driving style. Gas prices in examples are not current prices.

How to calculate MPG

Fill the tank, reset the trip meter, and drive as usual. At the next fill-up, add the same pump until it clicks off, and divide the miles on the trip meter by the gallons you pumped. The average of three or four fill-ups smooths out pump differences.

MPG = miles driven ÷ gallons used
Cost per mile = price per gallon ÷ MPG
Trip cost = (miles ÷ MPG) × price per gallon

Example: 360 miles on 12 gallons is 30 mpg. With gas at $3.50 a gallon, the cost per mile is 3.50 ÷ 30 = $0.117, or about 11.7 cents. To work out your share of a monthly gas bill, use the percentage calculator.

What a trip costs at different MPG

Distance25 mpg30 mpg35 mpg
100 miles$14.00$11.67$10.00
300 miles$42.00$35.00$30.00
500 miles$70.00$58.33$50.00
Gas at $3.50 a gallon, an example price. Trip cost = miles ÷ mpg × price.

For a round trip, double the miles. The Trip tab does it with one switch, and it splits the total between riders if you share the cost. Tolls, parking, and wear on the car are not in this number.

MPG to L/100 km and km/L

US mpgL/100 kmkm/L
2011.768.50
259.4110.63
307.8412.75
356.7214.88
405.8817.01
504.7021.26
L/100 km = 235.215 ÷ mpg, using the US gallon (3.785 liters). Lower L/100 km means better economy.
The UK imperial gallon is bigger than the US gallon, so a UK mpg figure is not the same as a US mpg figure. This calculator uses the US gallon.

What changes your fuel economy

  • Tire pressure below the number on the driver door sticker raises fuel use.
  • Highway speed matters: gas mileage usually drops as speed climbs above about 50 mph.
  • Air conditioning, heavy loads, and a roof carrier, even an empty one, lower the average.
  • Stop-and-go traffic and hard acceleration burn more than steady cruising.

The EPA fuel economy label on a new car shows tested city, highway, and combined mpg. Real driving often lands above or below those numbers, so measure your own with the tank-to-tank method.

Frequently asked questions

How do I calculate my car's MPG?

Divide the miles driven by the gallons added at the next fill-up. Driving 360 miles and refilling with 12 gallons gives 30 mpg.

How do I calculate gas cost for a trip?

Divide the miles by your mpg, then multiply by the price per gallon. For 300 miles at 28 mpg with gas at $3.45, that is 10.71 gallons and $36.96.

How do I calculate cost per mile?

Divide the price per gallon by your mpg. Gas at $3.50 in a car that gets 30 mpg costs about 11.7 cents per mile.

How do I convert MPG to L/100 km?

Divide 235.215 by the mpg. A car that gets 30 mpg uses 7.84 liters per 100 km. Use the converter tab for any value.

What is a good MPG?

It depends on the vehicle type. Compare your result with the combined mpg on your car's EPA label and with similar models.

Why is my real MPG lower than the sticker?

The label comes from standardized tests. Speed, weather, tire pressure, cargo, and short trips can all push real mileage below the number on the sticker.

Sources and method

Standard public-domain formulas. Every calculation is checked against independent numeric tests before it goes live.