Fuel Cost Calculator
Find out what a road trip or your daily commute costs in fuel, in any units, split between everyone in the car.
Only changes the CO2 estimate.
Don’t know your fuel economy? Work it out from a fill-up
Fill the tank, note the trip meter, drive, then fill up again. Enter the distance since the last fill and how much fuel the second fill took.
Home charging is usually cheapest; public rapid chargers often cost two to three times more.
Some energy is lost as heat while charging. About 85–95% is usual.
Rough world average. Use 0 for home solar.
For a commute, pick “Return” and 5 times a week.
How your fuel cost is worked out
Cost = distance × fuel used per km × price of fuel.
- 1
Fuel used
300 km × 7 ÷ 100= 21 L
- 2
Fuel cost
21 L × $1.00= $21.00
- 3
Trip cost
$21.00 fuel= $21.00
- 4
CO2 estimate
21 L × 2.31 kg≈ 48.5 kg CO2
Read more: the formula, worked examples, unit conversions, electric cars and CO2
Fuel cost depends on three things: how far you drive, how much fuel the car burns for each kilometre or mile, and what a litre or gallon costs. Multiply them together and add anything else you pay on the way, like tolls and parking. Sharing the car divides the bill.
The formula
fuel used (litres) = distance (km) × litres per 100 km ÷ 100
fuel cost = fuel used × price per litre
trip cost = fuel cost + tolls and parking
each person pays = trip cost ÷ people
yearly cost = trip cost × trips a week × 52
electric: energy from the plug = distance × kWh per 100 km ÷ 100 ÷ charging efficiency
Worked example
With the starting inputs, a 300 km drive in a car that uses 7 L/100 km burns 300 × 7 ÷ 100 = 21 litres. With fuel at €1.75 a litre that costs 21 × 1.75 = €36.75, or 36.75 ÷ 300 = €0.1225 a kilometre. Burning 21 litres of petrol gives off about 21 × 2.31 = 48.5 kg of CO2. (The starting price follows your currency: $1.00, £1.40, ₹100, AED 2.70 and so on a litre. Type in what you pay today.)
Add €12 of tolls and share the car between 3 people: (36.75 + 12) ÷ 3 = €16.25 each. With a 50 litre tank, the car goes 50 ÷ 7 × 100 = 714 km on a full tank, so there’s no need to stop for fuel.
Miles and gallons
A 200 mile trip in a car doing 30 MPG (US) uses 200 ÷ 30 = 6.67 US gallons. At $3.60 a gallon that is 6.67 × 3.60 = $24.00, or 12 cents a mile. A UK gallon (4.546 litres) is bigger than a US gallon (3.785 litres), so the same car does more “MPG” in the UK: 30 MPG (US) is 36 MPG (UK).
Commuting
Driving 20 km each way to work, 5 days a week, in the same 7 L/100 km car is 40 km a day and 2.8 litres. At €1.75 a litre that is €4.90 a day, €24.50 a week, €1,274 a year (260 trips) and about €106 a month. Pick “Return” and “5 times a week” in Advanced mode.
Electric cars
An electric car using 17 kWh/100 km needs 300 × 17 ÷ 100 = 51 kWh in the battery for the same 300 km. About 10% is lost while charging, so you pay for 51 ÷ 0.90 = 56.67 kWh. At €0.30 a kWh that is €17.00, which is €19.75 less than the petrol car. Choose “Compare both” in Advanced mode to see the saving per trip and per year.
Fuel economy conversions
| L/100 km | MPG (US) | MPG (UK) | km/L |
|---|---|---|---|
| 4 | 58.8 | 70.6 | 25.0 |
| 5 | 47.0 | 56.5 | 20.0 |
| 6 | 39.2 | 47.1 | 16.7 |
| 7 | 33.6 | 40.4 | 14.3 |
| 8 | 29.4 | 35.3 | 12.5 |
| 10 | 23.5 | 28.2 | 10.0 |
| 12 | 19.6 | 23.5 | 8.3 |
| 15 | 15.7 | 18.8 | 6.7 |
L/100 km = 235.21 ÷ MPG (US) = 282.48 ÷ MPG (UK) = 100 ÷ km/L. A lower L/100 km is better; a higher MPG or km/L is better.
CO2 estimates
Burning a litre of fuel gives off roughly 2.31 kg of CO2 for petrol, 2.68 kg for diesel and 1.51 kg for LPG. These are approximate tailpipe figures: the US EPA uses 8,887 g per US gallon of petrol (about 2.35 kg a litre), and UK government figures are a little lower because pump fuel contains some biofuel. For electric cars the CO2 depends on how your electricity is made. The 0.45 kg per kWh starting figure is a rough world average; it is far lower in countries with mostly hydro, nuclear or wind power, and higher where coal is used. Change it in Advanced mode.
Tips to spend less on fuel
- Your real economy is often 10–20% worse than the official figure, especially in town or at motorway speeds. The fill-up helper in Advanced mode works out your real number.
- Driving at 110 km/h (about 70 mph) instead of 130 km/h (80 mph) can cut fuel use by around a sixth.
- Correct tyre pressures, less weight and no roof box all help.
- Fuel prices vary a lot between stations; motorway stations are usually the dearest.
Starting prices are examples only, not live prices: enter today’s price where you fill up. CO2 figures are estimates. Fill-up stops assume you set off with a full tank (or full battery) and use it right down; in practice, plan to refuel with a quarter of a tank left. Checked 10 October 2026.
Common questions
How do I calculate the fuel cost of a trip?
Multiply the distance by your car's fuel use, then by the price of fuel. A 300 km drive at 7 L/100 km burns 21 litres, and at €1.75 a litre that costs €36.75. Add any tolls and parking, then divide by the number of people if you're sharing the car.
How do I convert MPG to L/100 km?
Divide 235.21 by MPG (US), or 282.48 by MPG (UK), to get litres per 100 km. For km per litre, divide 100 by the L/100 km figure. So 7 L/100 km is 33.6 MPG (US) or 40.4 MPG (UK). A lower L/100 km is better, while a higher MPG or km/L is better.
How much does it cost to commute by car?
Work out the return distance each day, then multiply by the days you drive. Driving 20 km each way, 5 days a week, in a 7 L/100 km car at €1.75 a litre costs €4.90 a day, €24.50 a week and about €1,274 a year. Pick Return and the trips a week in Advanced mode.
Is an electric car cheaper to run than a petrol car?
Often, but it depends on your prices. In the example, a 300 km trip costs €36.75 in petrol but €17.00 in an electric car using 17 kWh/100 km at €0.30 a kWh, including about 10% lost while charging. Choose Compare both in Advanced mode to use your own prices.
Why is my real fuel economy worse than the official figure?
Real economy is often 10–20% worse than the official figure, especially in town or at motorway speeds. Speed, tyre pressures, extra weight and roof boxes all play a part. The fill-up helper in Advanced mode works out your real number from the fuel you put in and the distance you drove.
How do I split petrol costs with friends?
Add up the fuel cost plus any tolls and parking, then divide by the number of people in the car. With €36.75 of fuel and €12 of tolls shared between 3 people, each pays €16.25. Set the number of people and the calculator shows each person's share as you type.
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