About Fuel Cost Calculator
Pick how your car's economy is quoted (km per litre, litres per 100 km, or miles per US or UK gallon), then enter the distance, the economy figure and the price of fuel. The calculator returns the total cost, the fuel needed, the cost per mile or per km and a per-person share. The sum is fuel needed × price: 500 km at 15 km per litre takes 33.33 litres, which costs 3,500.00 at 105 per litre. One thing to know before you start: the two mpg options expect a price per gallon, so a pump price per litre must be converted first, as shown in the table further down.
Petrol cost per mile by mpg
Calculated with the miles per UK gallon option at 1.40 per litre, which is 6.36 per imperial gallon. Fuel is in UK gallons.
| Fuel economy (UK mpg) | Fuel for 100 miles | Cost of 100 miles | Cost per mile |
|---|---|---|---|
| 25 mpg | 4 gallons | 25.44 | 25.4p |
| 30 mpg | 3.33 gallons | 21.20 | 21.2p |
| 35 mpg | 2.86 gallons | 18.17 | 18.2p |
| 40 mpg | 2.5 gallons | 15.90 | 15.9p |
| 45 mpg | 2.22 gallons | 14.13 | 14.1p |
| 50 mpg | 2 gallons | 12.72 | 12.7p |
| 55 mpg | 1.82 gallons | 11.56 | 11.6p |
| 60 mpg | 1.67 gallons | 10.60 | 10.6p |
| 70 mpg | 1.43 gallons | 9.09 | 9.1p |
The pence column is the cost of 100 miles divided by 100. The tool itself rounds Cost per mile to two decimals, so it shows 0.16 at 40 mpg and 0.13 at 50 mpg. With US gallons at 3.50 per gallon, 100 miles costs 17.50 at 20 mpg, 14.00 at 25 mpg, 11.67 at 30 mpg and 8.75 at 40 mpg.
Converting a price per litre to a price per gallon
Fuel is sold by the litre in the UK but economy is quoted in miles per imperial gallon. One imperial gallon is 4.54609 litres, so multiply the pump price by 4.546 and enter the result as the price when using the miles per UK gallon option.
| Price per litre | Price per UK gallon |
|---|---|
| 1.30 | 5.91 |
| 1.35 | 6.14 |
| 1.40 | 6.36 |
| 1.45 | 6.59 |
| 1.50 | 6.82 |
| 1.55 | 7.05 |
| 1.60 | 7.27 |
| 1.70 | 7.73 |
A US gallon is smaller, at 3.785 litres. Never mix a UK mpg figure with a US gallon price or the other way round.
Fuel cost by distance
Two reference cars: one using 6.5 litres per 100 km with fuel at 1.50 per litre, and one doing 40 miles per UK gallon with fuel at 6.36 per gallon.
| Distance | Economy and price | Fuel needed | Total cost |
|---|---|---|---|
| 32 km | 6.5 L/100 km, 1.50 per litre | 2.08 litres | 3.12 |
| 100 km | 6.5 L/100 km, 1.50 per litre | 6.5 litres | 9.75 |
| 400 km | 6.5 L/100 km, 1.50 per litre | 26 litres | 39.00 |
| 1,000 km | 6.5 L/100 km, 1.50 per litre | 65 litres | 97.50 |
| 2,000 km | 6.5 L/100 km, 1.50 per litre | 130 litres | 195.00 |
| 3,500 km | 6.5 L/100 km, 1.50 per litre | 227.5 litres | 341.25 |
| 22 miles | 40 mpg (UK), 6.36 per gallon | 0.55 gallons | 3.50 |
| 100 miles | 40 mpg (UK), 6.36 per gallon | 2.5 gallons | 15.90 |
| 180 miles | 40 mpg (UK), 6.36 per gallon | 4.5 gallons | 28.62 |
| 340 miles | 40 mpg (UK), 6.36 per gallon | 8.5 gallons | 54.06 |
| 500 miles | 40 mpg (UK), 6.36 per gallon | 12.5 gallons | 79.50 |
Prices here are example figures, not current pump prices. Enter today's price where you fill up for a real estimate.
Fuel cost formulas for each efficiency unit
km per litre or mpg: fuel needed = distance ÷ efficiency litres per 100 km: fuel needed = distance × efficiency ÷ 100 Total cost = fuel needed × price per litre or gallon Cost per mile or km = total cost ÷ distance Per person = total cost ÷ people
Litres per 100 km is a consumption figure, so a lower number is better and it multiplies rather than divides. To switch between systems: UK mpg × 0.354 = km per litre, US mpg × 0.4251 = km per litre, 282.48 ÷ UK mpg = litres per 100 km and 235.21 ÷ US mpg = litres per 100 km. A 40 mpg (UK) car therefore uses about 7.06 litres per 100 km. Ticking Return trip doubles the distance before any of these sums are done.
Worked trip examples in each unit
Return road trip split four ways (km per litre)
km per litre, Distance 500, Fuel efficiency 15, Price 105, Split between 4, Return trip ticked
Total cost 7,000.00, Fuel needed 66.67 litres, Distance 1,000 km, Cost per km 7.00, Per person 1,750.00
Long diesel run (litres per 100 km)
litres per 100 km, Distance 2000, Fuel efficiency 5.5, Price 1.60
Total cost 176.00, Fuel needed 110 litres, Cost per km 0.09
US highway drive shared by two (miles per US gallon)
miles per US gallon, Distance 300, Fuel efficiency 28, Price 3.50, Split between 2
Total cost 37.50, Fuel needed 10.71 US gallons, Cost per mile 0.13, Per person 18.75
UK motorway journey (miles per UK gallon)
miles per UK gallon, Distance 340, Fuel efficiency 50, Price 6.36
Total cost 43.25, Fuel needed 6.8 UK gallons, Cost per mile 0.13
6.36 per gallon is a pump price of 1.40 per litre multiplied by 4.546.
Electric car using the km per litre option
km per litre, Distance 300, Fuel efficiency 6 (km per kWh), Price 0.30 (per kWh)
Total cost 15.00, Fuel needed 50 (shown as litres, read as kWh), Cost per km 0.05
Why a real trip often costs more than the estimate
The result is only as good as the economy figure you enter. Official figures come from standardised test cycles, and everyday driving usually falls short of them. Sustained high motorway speeds, stop-start town traffic, short journeys on a cold engine, air conditioning, a roof box or bike rack, a full load of passengers and luggage, and under-inflated tyres all push consumption up.
For a figure you can trust, measure your own car. Fill the tank and reset the trip meter. At the next fill, note the distance covered and the litres added, then divide distance by litres for km per litre, or use the average shown on the car's trip computer over several tanks.
Fuel is also only one part of the cost of driving. Tolls, parking, tyres, servicing and depreciation are not included, which matters when you compare the result with a train or coach fare or set a mileage rate for sharing costs.
Things this calculator does not do
- Convert a litre price for the mpg options. Multiply by 4.546 for UK gallons or 3.785 for US gallons before entering it.
- Look up distances or routes. Take the distance from a map app or your odometer.
- Fetch live petrol or diesel prices. You enter the price you expect to pay.
- Show fractions of a penny or cent per mile. Cost per mile is rounded to two decimals, so enter the price in pence or cents (636 instead of 6.36) to read it as 15.90 pence per mile.
- Work backwards from a fuel budget to a distance. By hand, range = litres × km per litre.
- Weight the split. Per person divides the total evenly between the number of people entered, and the field is set up for 1 to 20.
How to get your result
- 1
Choose the Efficiency unit that matches your figure: km per litre, litres per 100 km, miles per US gallon or miles per UK gallon.
- 2
Enter the one-way Distance, in km for the metric options or miles for the mpg options.
- 3
Enter your Fuel efficiency in the unit you picked, for example 6.5 for litres per 100 km or 40 for mpg.
- 4
Enter Price per litre / gallon: per litre for the metric options, per gallon for the mpg options. For UK mpg, multiply the litre price by 4.546.
- 5
Set Split between to the number of people sharing, and tick Return trip to double the distance.
- 6
Read Total cost, Fuel needed, Distance, Cost per mile or km and Per person.