Fuel Cost Calculator
Calculate the fuel cost of any trip based on distance, fuel efficiency, and local fuel price.
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The fuel cost calculator works out what a journey costs in petrol or diesel, using distance, your car's consumption, and the pump price you are actually paying. Enter the distance, the fuel efficiency in litres per 100 km, and the price per litre. You get the litres used, the total cost, and the cost per 100 km. Fuel is one of the bigger variable costs of running a car and one of the least often worked out in advance. A 320 km run, roughly London to Manchester, in a car doing 8 L/100km at £1.40 a litre comes to about £36 each way, or £72 there and back. That is the kind of number worth having before you decide between driving, taking the train, or splitting a car with someone. Two conversions help if you think in imperial. Multiply miles by 1.609 for kilometres, so a 200 mile trip is about 322 km. For consumption, divide 282 by your mpg to get L/100km, so 45 mpg is about 6.3 L/100km. UK mpg uses imperial gallons, which is why the number is 282 and not the 235 you will see quoted against American mpg.
How to Use the Fuel Cost Calculator
The Fuel Cost Calculator is designed to give you an accurate answer in seconds. Follow these steps:
- 1Enter your distance (km) in the Distance (km) field. The minimum value is 1. The default is 100 km. Adjust this to match your specific situation.
- 2Enter your fuel efficiency (l/100km) in the Fuel Efficiency (L/100km) field. The valid range is 1 to 30. The default is 8 L/100km. Adjust this to match your specific situation.
- 3Enter your fuel price per litre in the Fuel Price per Litre field. The minimum value is 0.5. The default is £1.4. Adjust this to match your specific situation.
- 4Click Calculate to see your results instantly. The output updates as soon as you submit.
No account or sign-up required. All calculations run locally in your browser — nothing is stored or transmitted to any server.
Example Calculation
Here is what the Fuel Cost Calculator produces with its default values. Change any input above to recalculate instantly for your own figures.
Inputs
- Distance (km)100 km
- Fuel Efficiency (L/100km)8 L/100km
- Fuel Price per Litre£1.4
Results
- Fuel Used8.00 L
- Trip Cost£11.20
- Cost per 100 km£11.20
How It Works
Trip Cost = (Distance × Fuel Efficiency ÷ 100) × Fuel Price per Litre
The maths is a straight multiplication of distance, consumption and pump price, so it needs no external source, and the prices in the worked examples are round illustrative figures rather than quoted averages. For the current UK average, DESNZ publishes weekly road fuel prices at gov.uk/government/statistics/weekly-road-fuel-prices. For the official consumption figure for a specific model, the Vehicle Certification Agency publishes WLTP results at carfueldata.vehicle-certification-agency.gov.uk.
Formula: Trip Cost = (Distance × Fuel Efficiency ÷ 100) × Fuel Price Litres Used = Distance (km) × Fuel Efficiency (L/100km) ÷ 100 Trip Cost = Litres Used × Fuel Price per Litre Cost per 100 km = Fuel Efficiency × Fuel Price Example: a 350 km drive, about 217 miles, in a car using 8.5 L/100km, with fuel at £1.40 a litre. Litres used = 350 × 8.5 ÷ 100 = 29.75 L Trip cost = 29.75 × £1.40 = £41.65 Cost per 100 km = 8.5 × £1.40 = £11.90 The £1.40 is a round illustrative price rather than a live average, so put in whatever you last paid. Pump prices vary by several pence between supermarkets and motorway services, and that spread is large enough to change the answer. Double the distance for a return trip, and add the legs together first for a journey with stops. Real-world consumption usually runs above the official WLTP figure once traffic, load, tyre pressure and speed are accounted for, so if your trip computer gives you a long-run average, use that instead of the brochure number.
Frequently Asked Questions
How do I calculate fuel cost for a road trip?
Multiply the distance in kilometres by your car's consumption in L/100km, divide by 100 for the litres you will burn, then multiply by the price per litre. For example, 600 km at 9 L/100km is 54 litres, and at £1.40 a litre that comes to £75.60. If your distance is in miles, convert first by multiplying by 1.609, so 373 miles is about 600 km. The calculator handles all of it as you type.
What is good fuel efficiency for a car?
Rough bands, with the imperial mpg equivalent alongside. Under 6 L/100km, over 47 mpg, is excellent and typical of hybrids and small efficient cars. 6 to 8 L/100km, 35 to 47 mpg, is good and covers most family hatchbacks and small SUVs. 8 to 11 L/100km, 26 to 35 mpg, is average for larger cars and mid-size SUVs. 11 to 15 L/100km, 19 to 26 mpg, is high, which is where big SUVs, performance cars and older engines sit. Anything above 15 L/100km is under 19 mpg. Steady motorway running is usually more efficient than town driving because there is less stopping and starting, though that advantage falls away the faster you go.
How do I convert MPG to L/100km?
UK mpg is quoted in imperial gallons, so divide 282.5 by your mpg to get L/100km. A car doing 40 mpg is 282.5 ÷ 40 = 7.06 L/100km, and 55 mpg is about 5.1 L/100km. To go the other way, divide 282.5 by the L/100km figure. American mpg uses a smaller gallon and needs 235.2 instead, which is why the same car looks less economical in US reviews than in UK ones.
How can I reduce my fuel costs?
Keep tyres at the pressure in the handbook, because soft tyres make the engine work harder for the same distance. Ease off the accelerator and read the road far enough ahead that you brake early rather than hard. Take the roof box or bars off when you are not using them, since the drag costs you on every journey afterwards. Stay on top of servicing, particularly the air filter. On the motorway, sitting at 60 to 65 mph instead of pushing the limit makes a noticeable difference because drag climbs steeply with speed. None of these is dramatic alone, and together they are worth a few percent over a year. Shopping around on where you fill up often saves more than all of them.
Is the fuel cost calculator free?
Yes — free with no sign-up needed. Enter your trip distance, fuel efficiency, and local pump price for an instant cost estimate. All calculations run in your browser and no data is stored. For a return trip, double the distance figure, or run two separate calculations for legs with different distances.