How to use the Fuel Cost Calculator
- Enter the one-way distance and choose kilometers or miles.
- Enter your car’s fuel economy and pick its unit: L/100 km, km/L, US MPG or UK MPG.
- Enter the fuel price per litre or per gallon, and change the currency symbol if needed.
- Tick Round trip and set the number of people sharing to see the total and the cost per person.
Features
- Distance in kilometers or miles
- Economy in L/100 km, km/L, US MPG or UK MPG
- Price per litre, US gallon or UK gallon, in any currency
- Round-trip option and cost split between passengers
- Fuel needed in litres and gallons, plus cost per km or mile
- Remembers your units and car for next time
How the fuel cost is calculated
There are three steps: work out how much fuel the trip needs, convert it to the unit your price uses, then multiply.
- Fuel needed depends on how your car's economy is written:
- L/100 km: litres = distance (km) × economy ÷ 100
- km/L: litres = distance (km) ÷ economy
- MPG: gallons = distance (miles) ÷ MPG
- Cost = fuel needed × price per unit of fuel.
- Cost per person = cost ÷ number of people sharing.
Worked examples
A 300 km drive in a car that uses 6.5 L/100 km needs 300 × 6.5 ÷ 100 = 19.5 litres. At 1.80 per litre the fuel costs 19.5 × 1.80 = 35.10. As a round trip shared by three friends, that is 70.20 in total, or 23.40 each.
In US units, a 250-mile trip at 30 MPG needs 250 ÷ 30 ≈ 8.33 gallons. At $3.50 a gallon the fuel costs $29.17.
US gallons, UK gallons and litres
A US gallon is 3.785 litres, while an imperial (UK) gallon is 4.546 litres, about 20% more. So the same car shows a higher MPG figure in the UK than in the US: 30 MPG (US) is about 36 MPG (UK). Mixing them up is the most common mistake in trip calculations, so choose the right one in the unit menus. The calculator converts everything through litres internally, so you can combine any units, such as miles with a price per litre.
| L/100 km | km/L | MPG (US) | MPG (UK) |
|---|---|---|---|
| 4 | 25 | 58.8 | 70.6 |
| 6 | 16.7 | 39.2 | 47.1 |
| 8 | 12.5 | 29.4 | 35.3 |
| 10 | 10 | 23.5 | 28.2 |
| 12 | 8.3 | 19.6 | 23.5 |
To convert yourself: MPG (US) = 235.21 ÷ L/100 km and MPG (UK) = 282.48 ÷ L/100 km. Because L/100 km measures fuel used rather than distance covered, lower is better, while for km/L and MPG higher is better.
Making the estimate realistic
- Use real-world economy. Official ratings come from standardized tests, and many drivers see higher consumption on the road. If your dashboard shows average consumption, use that.
- Speed matters. Air resistance rises quickly with speed, so long stretches at high highway speeds use noticeably more fuel than the same distance at moderate speeds.
- Load and accessories. Passengers, luggage, roof boxes and air conditioning all raise consumption, as do hills and stop-and-go city traffic.
- Add a buffer. Budget around 10% extra for detours, traffic and finding parking.
Need to convert a distance first? Use the Length Converter. To compare fuel volumes, the Volume Converter handles litres and gallons.
Frequently asked questions
How do I calculate the fuel cost of a trip?
Work out the fuel needed from the distance and your car’s economy, then multiply by the fuel price. For example, 300 km at 6.5 L/100 km uses 19.5 litres, which costs 35.10 at 1.80 per litre.
What is the difference between US and UK MPG?
They use different gallons. A UK (imperial) gallon is 4.546 litres and a US gallon is 3.785 litres, so the same car gets about 20% more miles per UK gallon.
How do I convert L/100 km to MPG?
Divide 235.21 by the L/100 km figure for US MPG, or 282.48 for UK MPG. A car using 8 L/100 km does about 29.4 MPG (US) or 35.3 MPG (UK).
Can I use it for an electric car?
Yes, with a small trick: choose L/100 km, enter your car’s kWh per 100 km as the economy and the electricity price per kWh as the price per litre. The arithmetic is identical, and the "litres" figure is then kWh.
How do I split fuel costs with passengers?
Enter the number of people sharing the cost, including the driver if they pay a share. The calculator divides the total and shows what each person owes.