Fuel Cost Calculator
Trip fuel cost from distance, economy and price, in US, UK or metric units. 100% free, no signup. Everything runs in your browser.
Loading the tool…
Distance, fuel economy, fuel price: this fuel cost calculator turns those three numbers into what the trip will actually cost, with a round-trip toggle and a split between passengers so nobody argues about gas money in a parking lot.
Units are handled properly rather than approximately. US miles per gallon, UK miles per gallon and liters per 100 km are three genuinely different systems, and the US and UK gallon are not even the same size, a detail that quietly wrecks most casual conversions. Everything runs in your browser and nothing is uploaded.
How to use
- Choose your unit system: miles with US mpg, miles with UK mpg, or kilometers with L/100km.
- Enter the trip distance.
- Enter your vehicle's fuel economy.
- Enter the local fuel price per gallon or per liter.
- Toggle round trip if you are coming back the same way.
- Set the number of passengers splitting the cost and read the per-person share.
Why use our fuel cost calculator?
The part I got wrong first was the gallon. A UK gallon is 4.546 liters and a US gallon is 3.785, so a British car doing 45 mpg is really doing about 37 in American terms. My first draft used one conversion for both, and every UK estimate came out flattering by roughly 20 percent. Now the toggle treats them as the separate units they are, and the numbers survive contact with an actual fuel receipt.
Use your real-world economy figure, not the brochure one. Window-sticker numbers come from standardized tests, and your true mpg depends on speed, load, weather and how you drive. The US Department of Energy's fueleconomy.gov publishes official ratings alongside real-driver data for nearly every model sold in the US, and it is the best starting point if you do not know your car's honest number.
The passenger split settles the awkward conversation in advance. A 300-mile round trip at 30 mpg and $3.50 a gallon is $35 of fuel, which is $8.75 each with four aboard. Share the number before the trip and the money conversation is over before it starts.
The calculator only claims to know fuel, and I want to keep it that way. Tolls, parking, depreciation and the obligatory gas-station snacks are outside its jurisdiction, and I would rather leave them out than pad the estimate with invented guesses. Round trip is a toggle rather than an afterthought because forgetting the return leg is the single most common trip-cost mistake I know.
For converting between mpg and L/100km outside the context of a trip, the unit converter does straight conversions, and if you are driving abroad, the currency converter translates the pump price before this tool tallies the damage.
Who is this tool for?
Road trip planning is the obvious one. A 1,100-mile round trip in a car doing 28 mpg at around $3.60 a gallon is roughly $141 in fuel. Split four ways, that is about $35 each, which suddenly compares very favorably with four airfares, and now the drive-or-fly debate has a number in it instead of vibes.
Commute math is the quiet one. A 40-mile daily round trip at 28 mpg and $3.60 a gallon costs about $26 a week, which is over $1,200 a year, and that figure belongs in the same spreadsheet as the salary when you weigh a job offer against a longer drive. My salary converter helps with the other side of that equation.
Carpool fairness is where the split earns its keep. Same four coworkers, alternating drivers, one honest per-person number per week, zero simmering resentment. It works just as well for festival convoys and university runs home for the holidays.
It is also handy when choosing between your own cars for a long trip, because seeing the SUV cost $30 more than the hatchback over one weekend turns an abstract mpg difference into actual money.
Frequently asked questions
Fill the tank, reset the trip odometer, drive normally, fill again. Miles driven divided by gallons on the second fill is your true figure. Do it over two or three tanks and you will have a number the brochure never told you.
Different gallons. The imperial gallon is 4.546 liters, the US gallon 3.785, so the same physical car scores about 20 percent higher in UK mpg. Comparing them without converting is the classic error, and it is why the calculator asks which one you mean.
It is liters burned per 100 kilometers, standard in Canada, Australia and Europe, and lower is better. It feels inverted coming from mpg, but it makes cost math easier: multiply by the distance in hundreds of kilometers and by the price per liter, which is exactly what the calculator does.
No, fuel only, and that is deliberate. Depreciation, tires and maintenance mean the true per-mile cost of driving runs well above the fuel line, but those vary so much by car that any built-in guess would be fiction. Fuel is the part three numbers can honestly compute.
As accurate as your economy figure. Highway cruising beats the sticker, city stop-and-go and roof boxes fall below it, winter costs more than summer. Use a realistic mpg from your own driving and the estimate typically lands within a few dollars on a long trip.
My take: splitting fuel equally is the floor, since the owner also quietly pays for tires, insurance and depreciation. Many groups round the driver's share down or cover their food. The calculator gives the equal split, and generosity is yours to add on top.
No. Distances, prices and passenger counts stay in your browser and the arithmetic runs locally. I have no idea where you are driving, which is exactly as it should be.