Fuel Cost Calculator
Gas calculator for a trip: distance, your mpg or L/100 km and the fuel price give the trip cost, cost per mile and per passenger, for a commute or a road trip.
Every convention this page applies is named in the result rather than assumed. Your numbers stay in this browser.
Results
How to read this: the verdict describes how much room your numbers leave, not a decision or an offer. Change any input to see how much the result moves.
Assumptions and formula
Distance is converted to kilometres and economy to litres per 100 km, so the fuel needed is distance ÷ 100 × L/100 km. The price is converted to a per-litre figure and multiplied by the litres. The conversions use the defined values: a mile is 1.609344 km, a US gallon is 3.785411784 litres and an imperial gallon is 4.54609 litres.
The economy figure is taken as constant over the trip, so the result is the fuel bill at the quoted economy rather than a forecast; real consumption rises in traffic, on hills and in cold weather. Only fuel is costed — tolls, parking, wear and depreciation are not included. The economy you entered is restated in all four conventions so a figure from another country’s brochure can be checked.
Worked example
A 300 km trip in a car doing 7 L/100 km uses 21 litres; at $1.50 a litre that is $31.50, or 10.5 cents a kilometre. A 100-mile drive at 25 US mpg with fuel at $3.50 a US gallon uses 4 gallons and costs $14.00; as a round trip shared by four people it is $28.00, or $7.00 each. That same car doing 25 US mpg is 30 mpg in UK terms.
Frequently asked questions
Why is UK mpg different from US mpg?
Because the gallons are different. An imperial gallon is 4.546 litres and a US gallon is 3.785 litres, so the same car travels 20% further per imperial gallon: 40 mpg in the UK is 33.3 mpg in the US. A calculator with a single mpg box is wrong for one country. This one asks which gallon you mean and restates the economy in both, plus L/100 km and km/L.
How do I convert L/100 km to mpg?
Divide 235.215 by the L/100 km figure for US mpg, or 282.481 for UK mpg. So 7 L/100 km is 33.6 mpg US and 40.4 mpg UK. The two are reciprocals with a constant: lower is better in L/100 km, higher is better in mpg. The result table on this page shows all four conventions for whatever you entered.
How much does fuel cost per mile?
Fuel price per gallon divided by miles per gallon. At $3.50 a gallon and 30 mpg that is 11.7 cents a mile; at 20 mpg it is 17.5 cents. In UK terms, £1.45 a litre in a car doing 40 mpg is 16.5p a mile, because a UK gallon costs £6.59. The per-mile and per-kilometre figures here use your own numbers rather than a national average.
Does this include the true cost of driving?
No, only fuel. Tyres, servicing, insurance, depreciation and tolls typically push the full cost of a mile to three or four times the fuel alone, which is why mileage allowances (the IRS rate, HMRC’s 45p) are so much higher than the fuel figure. Use this for splitting the fuel on a shared trip or comparing routes; use an ownership-cost figure when deciding whether to drive at all.
How do I work out the gas cost for a trip?
Divide the distance by your car’s fuel economy to get the fuel used, then multiply by the price. A 300-mile drive at 30 mpg uses 10 gallons, which at $3.50 a gallon is $35. That is all a gas calculator for trip planning does, and a road trip gas calculator or gas cost calculator repeats it for each leg; a fuel calculator in litres does the same sum with L/100 km. A gas mileage calculator or mpg calculator works the other way round, dividing miles driven by gallons filled to tell you the mpg you actually got, which is often lower than the sticker figure. This page does both, in mpg or litres per 100 km.
Is this a trip cost calculator or only a fuel calculator?
A trip fuel cost calculator, strictly: it prices the fuel for the distance and nothing else. Tolls, parking and wear are outside it, so a trip cost calculator in the full sense would add those on top. What it does add is a cost per mile calculator view, the fuel cost divided by the distance, which is the figure to use when splitting a journey or claiming mileage, and an economy converter for mpg to l/100km and back, since the two conventions run in opposite directions and are easy to misread.