Fuel Cost

Turn a distance, a consumption figure and a pump price into what the drive will cost in fuel.

Runs on your deviceCalculatorsWorkingNo account needed

What this tool does

Fuel Cost converts everything you give it to a single base before doing any sums: the distance to kilometres, the economy to litres per 100 km, and the price to a price per litre. Litres burned is then the kilometres multiplied by that consumption figure and divided by a hundred, and the trip cost is those litres at the price per litre. Because the conversion happens first, the units you happen to think in never change the answer — 30 mpg and 7.84 L/100 km produce the same cost for the same drive.

The output restates every step in the units you might want to check it in, which is most of the point. You get the distance in km and miles, the economy simultaneously as L/100 km, km per litre, mpg (US) and mpg (UK), the fuel needed in litres and in both gallons, the price expressed per litre and per gallon, and the total broken down to a cost per km and per mile. Tick Round trip and the distance is doubled before any of that happens; set Split between to more than one and the total is divided evenly at the end.

Units get decided carefully, because getting one wrong is the failure mode of every fuel calculator. A unit written beside the value in the optional text box wins over the dropdown, and so does a unit carried by the field name — "miles: 100" is read as miles whatever the Distance unit selector says. The gallon distinction is handled explicitly: a UK gallon is 4.54609 litres against the US gallon's 3.785, so the same "30 mpg" is about 20% apart depending on which side of the Atlantic wrote it. Add "uk" or "imperial" beside the figure and it resolves to the imperial gallon. One catch is worth knowing: a unit the parser cannot place is not rejected. "distance: 100 furlongs" falls back without comment to whatever the Distance unit dropdown is set to, and "economy: 30 furlongs" takes the Economy unit dropdown instead — 30 L/100 km if you have left it alone. The Distance, Economy and Fuel price lines of the output name the unit each figure was finally read in, so check them there before trusting the total.

What it will not tell you is what the journey actually costs. One economy figure is held constant across the whole distance, so motorway cruising, town traffic, a loaded roof box, a headwind and a cold engine are all invisible to it — the answer is exact arithmetic on the number you supplied, not a prediction of the pump. It counts fuel and nothing else: no tolls, parking, ferries, servicing, tyres, insurance or depreciation, which is why the per-mile figure is not a mileage rate. There is no map and no price feed, so the distance and the price are both yours to enter, and the default 1.65 is a starting value rather than today's forecourt. Petrol and diesel only — every economy unit is volumetric, so there is nothing here to type kWh into and an electric car cannot be modelled. The whole calculation happens inside this browser tab: no request goes out, and there is no file to hand over in the first place.

How to use it

  1. Enter the distance for one leg. Kilometres or miles, chosen in the dropdown beside it. Tick Round trip to double the figure rather than typing the doubled number yourself.
  2. Give the economy in the unit you already know. L/100 km, km per litre, mpg (US) or mpg (UK). Take it from the trip computer or the manufacturer's combined figure; it has to be greater than zero.
  3. Enter the pump price and say what it is per. Litre, US gallon or UK gallon. Nothing is looked up, so use the price on the sign or the last receipt — the currency is simply whatever you typed in.
  4. Split it, if the cost is being shared. Split between takes a whole number of people, at least one, and divides the total equally. Everyone is assumed to be aboard for the full distance.
  5. Read the breakdown, or type the trip instead. The optional box accepts "field: value" lines — distance, economy, price, people, round trip — with aliases such as miles, mpg, consumption and passengers. A field it does not recognise is named back to you instead of being ignored.

Processing & privacy

Runs on your device. Your file is processed directly in this browser.

Common use cases

Deciding between the car and the train

Put the fuel figure next to the fare. It is only the fuel, so add parking and tolls yourself before calling the drive cheaper.

Settling up after a lift share

Set Split between to the number of passengers and the per-person line gives an even share of the fuel for everyone to pay back.

Comparing two cars for the same journey

Hold the distance and price steady and change only the economy. The difference in trip cost is what the more frugal car is actually worth over that drive.

Budgeting a holiday drive

Enter the one-way distance, tick Round trip, and the doubling is applied before the litres are worked out so the return leg is never forgotten.

Reading a foreign economy figure

An American review quoting 30 mpg and a European one quoting 7.8 L/100 km are describing nearly the same car. Enter either and the output prints both.

Questions

Is any of this sent anywhere?
No. The conversion and the arithmetic run in this browser tab, so the distances you drive and the prices you pay are not transmitted or logged anywhere. Once the page is open you can drop the connection and it will still calculate — but the page has to be fetched from the site first, as there is no offline copy installed on your machine.
What currency are the amounts in?
Whatever the pump price you typed was in; nothing is converted between currencies, so pounds in means pounds out. Figures print without any symbol — the trip cost, the per-gallon prices and each person's share to two decimals in your locale's number formatting, and the cost per km and per mile to three, because a rate that small would otherwise round to nothing. A price entered per gallon is restated per litre at two decimals for display, while the total behind it uses the unrounded figure.
Does it know the current fuel price?
No, and it does not try to. There is no price feed, so the 1.65 you start with is a placeholder to be replaced with the figure from the forecourt sign, a receipt or a fuel price site you trust.
Is mpg the US or the UK gallon?
Whichever you choose. The dropdown offers both, and in the text box "economy: 30 mpg" is read as US while "economy: 30 mpg uk" or "economy: 30 mpg imperial" is read as the imperial gallon. Keep the unit attached to the number: the shorthand field name "mpg: 30" pins the value to the US gallon by itself, and a stray "uk" written after it there is not picked up. The gap is around 20%, so it is worth being explicit.
Will the trip really cost this?
Rarely to the penny. The calculation applies one consumption figure evenly across the distance, while real use swings with speed, traffic, gradient, load, tyre pressure and how cold the engine starts. Use your own observed average rather than the brochure number if you want the estimate to land close.
Can I use it for an electric car?
No. Every economy unit here is volumetric — litres and gallons — so there is no way to enter kWh per 100 km or miles per kWh, and no way to enter a price per kWh.
Does the figure include tolls, parking or wear?
No. It is fuel and only fuel. Tolls, congestion charges, ferries, parking, servicing, tyres and depreciation are all outside it, which is also why the per-mile number should not be treated as a reimbursement rate.
What counts as a valid input?
Distance and economy must both be greater than zero, the price can be zero but not negative, and the number of people has to be a whole number of one or more. Anything else is refused with a message naming the field.

Related tools