MPG

Fuel price ($/gal)

Monthly miles

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Every figure above is calculated locally in your browser from the assumptions shown. No inputs are sent anywhere. See the methodology section below for the formulas used.

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Cost per mile at 12 mpg vs 30 mpg and city or highway — 12 mpg costs $0.300 per mile, 2.5x the 30 mpg figure.

Method & verification

How This Tool Works

Calculation Method

Cost per mile = Fuel price ÷ MPG

Site methodology

BoringToolsKit methodology and verification standard

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The Division Behind the Number

Cost per mile is just price divided by fuel economy. If gas is $3.60 per gallon and your car averages 30 mpg, one gallon buys 30 miles, so each mile costs $3.60 / 30 = $0.120. A 900-mile month then costs 900 x $0.120 = $108, or about $1,296 per year.

The division also shows you which lever moves faster. Cutting price from $3.60 to $3.30 at 30 mpg saves $0.01 per mile. Upgrading from 30 to 33 mpg at $3.60 saves $0.036 per mile, roughly triple the effect. That is why a $500 tune-up or tire-pressure fix that lifts real mpg by 2 to 3 often beats bargain hunting at the pump.

Watch the rounding, though. At 12 mpg the same $3.60 gas costs $0.300 per mile, so a 900-mile month is $270. The calculator shows three decimals because a per-mile figure like $0.125 looks identical to $0.120 once rounded to cents, but over 12,000 miles a year that is a $60 difference.

Where the Number Breaks Down

The formula assumes one blended mpg figure. Real drivers do not get one. City stop-and-go driving can run 20 to 25 percent below your highway figure, so a car rated 30 mpg overall might cost $0.150 per mile in town versus $0.115 on the interstate. If most miles are short urban trips, run the calculator with your city mpg for a more honest figure.

It also counts fuel only. AAA's 2024 driving cost study put total ownership cost for a midsize sedan near $0.65 to $0.70 per mile once depreciation, insurance, maintenance, and tires are added. Depreciation alone runs about $0.25 to $0.30 per mile on a new car, more than double the fuel cost. That is why the IRS rate sits near $0.70: if you are comparing against driving-for-work reimbursements, fuel is roughly a quarter of the real number.

Finally, the price input is a snapshot. US regular gas moved between roughly $3.00 and $5.00 per gallon in recent years, a swing that changes per-mile cost by 40 percent or more at the same mpg. Re-run the calc when local prices move by more than about $0.20 per gallon.