Enter your miles, MPG, and gas price. Compare vehicles and see your real monthly fuel cost.
Enter the miles you drive in a month, the price at your usual station, and your car's average MPG. The page returns monthly and annual fuel cost, the gallons you burn, and your cost per mile. The second MPG field compares a different vehicle, which is the number people actually want when they are thinking about trading a car in.
Use your real MPG, which you can work out from two fill-ups: miles driven divided by gallons added. The dashboard figure is usually optimistic, sometimes by several miles per gallon.
1,200 miles a month, gas at $3.50 a gallon, a car that averages 28 MPG, compared against one that does 42:
| Vehicle | Monthly | Yearly |
|---|---|---|
| 28 MPG | $150.00 | $1,800.00 |
| 42 MPG | $100.00 | $1,200.00 |
| Difference | $50.00 | $600.00 |
The 28 MPG car uses 42.9 gallons a month and costs 12.5 cents a mile. The 42 MPG car uses 28.6 gallons and costs 8.3 cents. Saving $600 a year is real money, but it does not pay for a newer car on its own: against a $12,000 difference in price it takes twenty years of driving at these prices to break even on fuel alone.
Cost per mile is the most portable number on the page. At 12.5 cents a mile, a 30-mile round trip costs $3.75 in fuel and a 400-mile weekend costs $50. That is a much easier way to think about a trip than watching the tank gauge, and it makes the comparison between two cars honest, because it does not depend on how much you drive.
The improvement from 28 to 42 MPG is 14 miles per gallon, which sounds like a third. The fuel saving is a third, and it is worth $600 a year. The same 14 MPG improvement from 42 to 56 would save only $250 more, because the gallons you avoid get smaller as the number gets larger. MPG is not a linear scale in savings, which is why the label alone cannot tell you which upgrade is worth it.
Fuel is one line of car costs. Insurance, maintenance and depreciation are usually larger, and the ownership calculator adds them together if you want the number that decides whether to keep the car.
Manufacturers measure under ideal conditions, and short trips with cold engines use more fuel than the test cycle. Two fill-ups and a division will give you the real number.
Yes, above about 50 mph the cost per mile rises steeply because aerodynamic drag grows with the square of speed. Dropping 10 mph on a highway run is the cheapest fuel saving available.
Only if your engine is designed for the higher octane. In a car that specifies regular, premium buys nothing but a higher price.
Miles divided by MPG, times the price per gallon. The road trip calculator does the same thing with lodging and food added.
No, the structure is the same with a different price per unit. The EV comparison uses cents per mile so the two can be put side by side.
Miles divided by MPG is the whole formula. The MPG should come from a tested figure or from your own gallons.
Last updated: November 2, 2026. Reviewed by David Liu.