Fuel Cost Calculator
Enter a distance, your fuel economy in any unit, and a fuel price to get the fuel needed and the total cost, with a round-trip toggle and a split-between-people option.
EIA weekly average, week of September 14, 2026 -- a starting point, not your local price.
People sharing the cost.
Total fuel cost
$37.49
Fuel needed
10.7 gal
40.6 L
Cost per mile
$0.12
$0.08 / km
Distance
300 mi
483 km
How it's calculated
Distance is converted to kilometers (doubled first if round trip is on), and fuel economy -- in whichever of the four supported units you entered -- is converted to liters per 100 km, the engine's shared internal unit:
fuel needed (L) = distance (km) ÷ 100 × economy (L/100km)
cost = fuel needed (L) × price ($/L)
Distance and volume conversions use the exact definitional constants a mile, a US gallon and a UK (imperial) gallon are fixed to (International Yard and Pound Agreement (1959); US NIST Handbook 44; UK Weights and Measures Act 1985) -- there's no rounding drift between units.
Worked example
The calculator's own defaults: a 300-mile one-way trip at 28 mpg (US), with gas at $3.50/gal.
| Distance | 300 mi (483 km) |
| Fuel needed | 10.7 gal (40.6 L) |
| Cost per mile | $0.12 |
| Total cost | $37.49 |
Plug the same numbers into the calculator above and it lands on the same result to the cent; that reconciliation is checked in the site's own test suite, not just written here.
Frequently Asked Questions
How is fuel cost calculated?
Distance is converted to kilometers, your fuel economy is converted to liters per 100 km (whatever unit you entered it in), and the two are multiplied to get liters of fuel needed. That's multiplied by your price per liter to get total cost. It's the same engine used as a fuel price calculator on every other page of this site -- enter a price, get a cost.
What fuel-economy units does this accept?
Miles per gallon (US), miles per gallon (UK -- the imperial gallon is about 20% larger, so mpg UK numbers run higher for the same car), liters per 100 km, and kilometers per liter. Pick whichever your vehicle's manual or dashboard already shows -- there's no need to convert it yourself first. The Fuel Economy Converter handles that conversion directly if you just want the number, not a cost.
Does this include tolls, parking or other trip costs?
No -- this is fuel only. For a trip with multiple legs and tolls, use the Trip Gas Cost Calculator, which adds toll costs to the fuel total before splitting between passengers.
Where does the fuel price come from?
Nowhere by default -- type in the price you actually pay. The price dropdown is a convenience: it fills in a real, dated starting point from US Energy Information Administration, Gasoline and Diesel Fuel Update (week of September 14, 2026), national average and the specific states and cities EIA reports weekly, but every number is yours to overwrite before you rely on it.
How accurate is the fuel-needed number?
It's an estimate; real consumption varies with driving style, load, terrain, tire pressure and weather -- highway cruising and stop-and-go city traffic can both differ meaningfully from a vehicle's rated or manually-calculated average. For your actual number, use the MPG Calculator on a real fill-up rather than a manufacturer estimate.
These are estimates; real consumption varies with driving, load and conditions. This site isn't affiliated with any vehicle manufacturer, utility, or the US Energy Information Administration -- see the Terms.