What this calculator does
Knowing how much fuel actually costs per kilometre turns an abstract consumption figure into a number you can budget against: what a commute costs each week, what a road trip will cost before you leave, or how two vehicles compare once petrol prices are factored in rather than just the litres burned.
The calculation starts from your car’s consumption rate, in litres per 100 kilometres, which you can get from a trip computer, a fill-up log, or the fuel consumption calculator if you only have a distance and a fuel amount. From there it is just distance travelled, litres used, and the price paid per litre.
The formula
Multiply the distance by the consumption rate and divide by 100 to get litres required, then multiply by the price per litre for the total cost. Dividing that total by the distance again gives a cost-per-km figure for quick comparisons.
| Term | Meaning |
|---|---|
| L/100km | Litres of fuel used per 100 kilometres travelled, the standard way consumption is quoted outside the US. |
| Cost per km | Total fuel cost for the trip divided by the distance, useful for comparing vehicles or routes directly. |
| Price per litre | The pump price on the day, which this calculator leaves fully editable since it changes constantly. |
The inputs explained
| Field | What to enter |
|---|---|
| Distance (km) | The distance for the trip or period you are costing, in kilometres. |
| Fuel consumption (L/100km) | Your vehicle’s consumption rate in litres per 100km. Check the trip computer, owner’s manual, or work it back from a recent fill-up. |
| Price per litre ($) | Current price per litre at the pump. This changes often, so update it before relying on the result. |
When to use it
Budgeting a road trip
Entering the total planned distance for a multi-day trip gives an upfront fuel budget, before other costs like tolls or accommodation are added on top.
Costing a daily commute
A fixed daily round-trip distance, multiplied out over a working week or month, turns a per-litre petrol price into a concrete weekly or monthly fuel bill.
Comparing two vehicles
Two cars with different consumption rates but the same trip distance and fuel price will show different total costs directly, without needing to convert consumption figures by hand first.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How trip cost changes with distance
The same consumption rate and fuel price applied across a range of trip distances.
| Distance | Total fuel cost | Litres needed |
|---|---|---|
| 50 km | $6.94 | 3.75 L |
| 100 km | $13.88 | 7.50 L |
| 250 km | $34.69 | 18.75 L |
| 500 km | $69.38 | 37.50 L |
| 1,000 km | $138.75 | 75.00 L |
| 2,000 km | $277.50 | 150.00 L |
How trip cost changes with the fuel price
A fixed 400km trip at a range of fuel prices per litre.
| Price per litre | Total fuel cost | Cost per km |
|---|---|---|
| $1.50 | $45.00 | $0.11 |
| $1.65 | $49.50 | $0.12 |
| $1.85 | $55.50 | $0.14 |
| $2.00 | $60.00 | $0.15 |
| $2.20 | $66.00 | $0.17 |
| $2.50 | $75.00 | $0.19 |
Questions
How is this different from the fuel consumption calculator?
The fuel consumption calculator works out your actual L/100km, km/L or mpg rate from a distance and fuel used. This calculator takes that rate as a known input and turns it into a dollar cost for a distance or trip, which is a separate, later step.
Where do I find my car’s L/100km figure?
Most modern cars display it on the trip computer. Otherwise, fill the tank, reset the trip odometer, drive normally until the next fill-up, and divide litres added by distance travelled, times 100.
Does this account for changing fuel prices during a long trip?
No, it uses one price per litre for the whole calculation. For a trip spanning regions with different prices, run it separately for each leg with its local price.
Why does cost per km look like such a small number?
Fuel is priced per litre but a car only uses a fraction of a litre per kilometre, so the per-km cost is naturally a small decimal even though the total trip cost can be substantial.
If you need to work out your consumption rate first, use the fuel consumption calculator. For unit conversions between mpg and L/100km, see the relevant conversion calculator.