Fuel cost calculator
Distance, MPG, gas price. See the gallons burned and what the trip costs before you drive it.
Budgeting a trip with the cost-per-mile figure
The headline cost answers "what will this trip cost me", but the cost-per-mile stat is the one worth memorizing, because it prices every future decision. At 30 MPG and $3.50 gas, driving costs about 11.7 cents per mile in fuel. Once you know your own figure, side quests price themselves: the scenic detour that adds 60 miles costs about seven dollars, and the debate over which of two routes to take usually turns out to be worth less than a coffee.
Use a pessimistic MPG. A loaded car with a roof box, a headwind, and 75 mph cruise speeds will run meaningfully below its EPA sticker. Knocking 10% off your usual number costs you nothing and keeps the estimate honest. If your dashboard shows a long-term average MPG, that number beats the sticker every time, because it already includes how you actually drive.
The split field settles carpools before anyone is trapped in the car together. Agree on the "Each pays" number up front, and note that splitting fuel evenly is generous to the driver in appearance only: fuel is just part of what the car costs to run. Tires, oil, and depreciation are real, which is why standard mileage reimbursement rates run several times higher than fuel-only cost per mile. For a friend trip, splitting fuel is fine. For anything resembling business use, fuel math undercounts.
A road trip, worked through
Three friends drive 450 miles each way in a car that really gets 28 MPG, with gas at $3.89. Enter 450, 28, 3.89, split between 3, and switch the toggle to round trip. The calculator doubles the distance to 900 miles, divides by 28 to get 32.14 gallons, and multiplies by $3.89 for a total of $125.04. Cost per mile comes out to $0.139, and each person pays $41.68. That is the real number to compare against three bus tickets or a flight, and it is usually a closer contest than people expect once you add a checked bag or two.
What the calculator computes
The chain is short: distance times the round-trip multiplier, divided by MPG, gives gallons; gallons times price gives cost; cost divided by total miles gives the per-mile figure, shown to three decimals because the third digit matters at this scale. The even split divides the total by the head count. The formula line under the result restates your inputs so a passenger can sanity-check them. Because the arithmetic carries no units of its own, metric drivers can enter kilometers, km per liter, and price per liter and get a correct total in their own currency.
What it does not know
This is a fuel-only model. Tolls, parking, and the extra quart of oil an older engine drinks on a long haul are on you to add. It assumes one constant MPG for the whole trip, so a route that is half city crawl and half interstate is best entered with a blended figure. It also treats the gas price as fixed, and on a multi-state drive prices can swing 50 cents or more per gallon; using the price from the expensive end of the route builds in a small cushion. Elevation, weather, and a trunk full of camping gear all push real consumption around in ways no calculator sees.
Frequently asked questions
How is trip fuel cost calculated?
Distance divided by your vehicle MPG gives gallons used; multiply by the price per gallon. A 300-mile trip at 30 MPG and $3.50/gal burns 10 gallons and costs $35.
What MPG should I use, city or highway?
For mostly-interstate trips use your highway figure; for mixed driving use the EPA combined number. Real-world MPG is often 10% below the sticker, so rounding your MPG down gives a safer estimate.
Does this work with kilometers and liters?
The math is unit-agnostic: enter kilometers as distance, your consumption converted to km per liter, and price per liter, and the result is in your currency per trip.