Annual Fuel Cost Calculator
Enter how far you drive, how much of it is city driving, and each vehicle's city and highway MPG and fuel price.
Vehicle A combined MPG
25 mpg
Vehicle A fuel per year
600 gal
Vehicle A fuel cost per year
$2,100.00
Vehicle A fuel cost per month
$175.00
Vehicle B combined MPG
49.1 mpg
Vehicle B fuel per year
305.6 gal
Vehicle B fuel cost per year
$1,069.69
Vehicle B fuel cost per month
$89.14
Vehicle A minus vehicle B, per year
$1,030.31
Vehicle A minus vehicle B, per month
$85.86
How it works
Each vehicle's city and highway MPG are combined into one figure for your mix of driving. Because MPG is distance per gallon, the combination is a harmonic mean weighted by the share of miles in each: the gallons used per mile in the city and on the highway are averaged, then turned back into MPG. This is how EPA builds the combined figure on a fuel economy label, with 55% city and 45% highway.
Yearly fuel is the miles per year divided by the combined MPG, and the yearly cost is those gallons times the fuel price. The monthly figure is the yearly cost divided by 12.
The last two results are vehicle A's cost minus vehicle B's. A positive amount means vehicle A costs more to fuel; a negative amount means it costs less. When the two cost the same per mile the difference is exactly zero.
Formula
s = city share % ÷ 100 combined MPG = 1 ÷ (s ÷ city MPG + (1 − s) ÷ highway MPG) gallons/year = miles per year ÷ combined MPG cost/year = gallons/year × fuel price cost/month = cost/year ÷ 12 difference = cost/year A − cost/year B
Example
At 15,000 miles a year with 55% city driving, vehicle A (22 city, 30 highway) combines to 1 ÷ (0.55 ÷ 22 + 0.45 ÷ 30) = 25.0 mpg. It burns 600 gallons, which at $3.50 a gallon is $2,100 a year, or $175.00 a month.
Vehicle B (50 city, 48 highway) combines to 49.1 mpg, burns 305.6 gallons and costs $1,069.69 a year ($89.14 a month). Vehicle A costs $1,030.31 more a year, $85.86 a month.
Assumptions and limitations
- MPG is held at the city and highway figures you enter. EPA label values are estimates; actual mileage varies with driving style, speed, load, weather, maintenance and vehicle condition.
- Fuel prices are inputs held constant for the year; the defaults are illustrative, not current market prices.
- Only fuel is counted. Maintenance, insurance, depreciation, registration and financing are not included.
- Results are an estimate for comparison, not a quote and not financial advice.
Frequently asked questions
Why not just average the city and highway MPG?
An arithmetic average overstates mileage. Fuel used is miles divided by MPG, so the low-MPG part of the driving weighs more than its share of miles. 40 CFR 600.210-12 has EPA harmonically average the city and highway values, weighted 0.55 and 0.45, for the combined label figure.
Where do the 15,000 miles and 55% city defaults come from?
They are the assumptions on EPA fuel economy labels and fueleconomy.gov: annual fuel cost there is based on 15,000 miles a year, 55% city and 45% highway driving. Your own mileage and mix can be entered instead.
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