8.2 L/100 km · 15¢ a mile · $149 a month
How the calculator works
Miles per gallon is the distance divided by the fuel used. The most accurate way to measure it is the fill-to-fill method: fill the tank until the pump clicks off, reset the trip odometer, drive normally, then fill again at the same pump if you can. The gallons from the second fill are what the car used for the miles on the trip meter. Averaging three or four tanks gives a steadier number than a single one, because pumps do not click off at exactly the same level every time.
Cost per mile is the gas price divided by your MPG. At $4.27 a gallon, the U.S. average for regular in the week of October 26, 2026 according to the Energy Information Administration, a car that gets 30 MPG spends 14 cents on fuel for every mile. The monthly figure multiplies that by the miles you enter.
Cost per mile at $4.27 a gallon
| MPG | L/100 km | Cost per mile | Per 1,000 miles | Per year (12,000 mi) |
|---|---|---|---|---|
| 15 | 15.7 | 28¢ | $285 | $3,415 |
| 20 | 11.8 | 21¢ | $213 | $2,561 |
| 25 | 9.4 | 17¢ | $171 | $2,049 |
| 30 | 7.8 | 14¢ | $142 | $1,708 |
| 35 | 6.7 | 12¢ | $122 | $1,464 |
| 40 | 5.9 | 11¢ | $107 | $1,281 |
| 50 | 4.7 | 9¢ | $85 | $1,025 |
The jump from 20 to 30 MPG saves far more than the jump from 40 to 50, even though both are 10 MPG. That is because fuel used falls with the inverse of MPG: going from 20 to 30 MPG saves 200 gallons over 12,000 miles, while going from 40 to 50 saves only 60.
Questions
How do I calculate my gas mileage?
Fill the tank and reset the trip meter. At the next fill-up, fill the tank again and note the gallons it took. Divide the miles on the trip meter by those gallons. 300 miles on 10 gallons is 30 MPG.
Why is my MPG lower than the EPA rating?
EPA numbers come from standard tests. Cold weather, short trips, high highway speeds, roof racks, underinflated tires, heavy loads and idling all lower real-world mileage, often by 10 to 20 percent in winter.
How do I convert MPG to liters per 100 km?
Divide 235.21 by the MPG. 30 MPG is about 7.8 L/100 km. The calculator shows both.
What is a good MPG?
For a gasoline car in 2026, many compact sedans are rated in the 30s combined, compact SUVs in the high 20s to low 30s, full-size pickups around 20, and hybrids in the 40s or 50s. Compare your figure with the EPA rating for your exact model on its MPG page.
Estimates for planning only. Gas price: U.S. Energy Information Administration, weekly U.S. regular retail price. Your result depends on how accurately the tank is filled.