How to work out the fuel cost of a trip
The maths is short. Take the distance in kilometres, divide by 100, multiply by your car's fuel use in litres per 100 km, then multiply by the price you pay per litre:
Trip cost = (km ÷ 100) × L/100km × price per litre
So a 100 km trip in a car that uses 8 L/100km, with fuel at $2.00 a litre, costs (100 ÷ 100) × 8 × $2.00 = $16.00. Toggle the return-trip option to double the distance, and split the cost between passengers when you carpool.
Cost per kilometre, and why it matters
Cost per km strips out the trip length so you can compare cars and journeys on a level footing. It is just your fuel use divided by 100, times the pump price. A frugal hatch at 6 L/100km costs about $0.12 per km at $2.00 a litre, while a large 4WD at 13 L/100km costs $0.26. Over a year of driving, that gap adds up fast.
Your commute over a week and a year
One trip rarely tells the full story. Switch to Regular commute and enter your trips per week to see the weekly and yearly cost. The yearly figure is the weekly cost times 52. Seeing the annual number is often the moment a short drive stops looking cheap, and it is worth checking against the rest of your recurring spend.
Rough fuel cost per 100 km
| Fuel use | At $1.90/L | At $2.00/L |
|---|
| 6 L/100km | $11.40 | $12.00 |
| 8 L/100km | $15.20 | $16.00 |
| 10 L/100km | $19.00 | $20.00 |
| 13 L/100km | $24.70 | $26.00 |
Figures are for a 100 km trip and round to the nearest cent. Enter your own fuel use and price above for an exact result.
Frequently asked questions
How do I calculate the fuel cost of a trip?
Use the formula: trip cost = (distance in km ÷ 100) × fuel use in L/100km × price per litre. For a 100 km trip in a car using 8 L/100km at $2.00 a litre, that's (100 ÷ 100) × 8 × $2.00 = $16.00. This calculator does the maths for you and shows the litres used as well.
How much does fuel cost per kilometre?
Cost per km is your fuel use divided by 100, times the pump price. At 8 L/100km and $2.00 a litre, that's (8 ÷ 100) × $2.00 = $0.16 per km. A thirstier car at 12 L/100km costs $0.24 per km at the same price. The calculator shows your cost per km next to the headline figure.
How do I work out my weekly and yearly fuel cost for commuting?
Switch the calculator to 'Regular commute' and enter how many trips you drive each week (a daily return commute is 10 trips). It multiplies your cost per trip by trips per week for the weekly figure, then by 52 for the yearly total. A 30 km each-way commute five days a week (10 trips) at 8 L/100km and $2.00 a litre runs about $2,496 a year.
What fuel efficiency should I enter?
Enter your car's fuel use in litres per 100 km (L/100km). Most small petrol cars sit around 6 to 8 L/100km, mid-size cars 8 to 10, and larger SUVs or utes 10 to 14. Your trip computer usually shows a real-world figure, which beats the sticker number. Diesels are often lower. Change the value to match your car.
What is a good fuel economy in L/100km?
Lower is better. Under 5 L/100km is very efficient, typical of hybrids and small diesels. Around 6 to 8 is good for a modern petrol car. Above 12 is thirsty, common in big SUVs, 4WDs and older vehicles. Electric cars use no petrol at all, which is why running costs differ so much.
What is the average petrol price in Australia?
Pump prices move with global oil prices and the local discounting cycle, so they swing week to week and between states. As a rough guide, unleaded (ULP 91) has recently sat near $1.90 to $2.00 a litre, with premium and diesel higher. Check a fuel app for today's price near you, then enter it above for an accurate figure.
This tool is a guide, not financial advice. Fuel use and pump prices vary, so treat the result as an estimate.
