What this calculator does
Fuel cost for a trip comes down to three numbers: how far you are going, how much fuel the car uses per 100 km, and what the fuel costs per litre. Multiply the first two together to get litres, multiply by the third to get the cost. Everything else on this page is a convenience laid on top of that.
The figure worth checking is the consumption one. Manufacturer combined-cycle numbers are optimistic for most real driving, and a car quoted at 6.5 L/100km may well return 8 on a loaded highway run with the air conditioning going. Working from your own recent fill-ups gives a far more useful answer than working from the brochure.
The formula
Litres used is the distance multiplied by the consumption figure and divided by 100, since consumption is quoted per 100 km. Fuel cost is that litre count multiplied by the price per litre. Cost per person divides the total by the number of people sharing, and driving time is distance divided by average speed, which is time in motion and excludes stops.
| Term | Meaning |
|---|---|
| Consumption | Fuel used per 100 km, the standard metric measure. A lower number means a more efficient car. |
| Cost per kilometre | Total fuel cost divided by distance, useful for comparing routes or for reimbursement at a fuel-only rate. |
| Average speed | Distance divided by time in motion. Realistic highway averages sit well below the speed limit once traffic and corners are included. |
| Cost per person | The total split evenly among everyone sharing the car, which is what makes driving cheap per head and expensive alone. |
The inputs explained
| Field | What to enter |
|---|---|
| Distance (km) | The one-way distance of the trip in kilometres. Double it for a return journey. |
| Consumption (L/100km) | Fuel consumption in litres per 100 km. Your own average from recent fill-ups is more accurate than the manufacturer figure. |
| Fuel price ($/L) | The price per litre you expect to pay. It varies by region and over time, so it is an input rather than a fixed value. |
| Average speed (km/h) | Average speed in km/h, used only for the driving time. This is time in motion and does not include stops or breaks. |
| People sharing | How many people are sharing the cost, used only to split the total. |
When to use it
Comparing driving against flying or the train
A fair comparison needs the fuel cost per person, not the total, since a car carrying four splits its cost four ways while a ticket does not. That is often the number that decides it.
Settling up on a shared road trip
Distance, consumption and the price actually paid give a total that everyone can see the working for, which makes splitting it a much shorter conversation.
Budgeting a long drive
A long trip run at a few different fuel prices shows how much the total moves with the pump price, which is worth knowing before committing to a route that crosses an expensive region.
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 much does fuel consumption change the cost of a long trip?
The same 850 km journey in cars of differing efficiency, from an economical small car to a large four-wheel drive.
| Consumption | Fuel cost | Fuel used | Cost per person |
|---|---|---|---|
| 5 L/100km | $82.88 | 42.5 litres | $41.44 |
| 6 L/100km | $99.45 | 51.0 litres | $49.73 |
| 7.5 L/100km | $124.31 | 63.8 litres | $62.16 |
| 9 L/100km | $149.17 | 76.5 litres | $74.59 |
| 12 L/100km | $198.90 | 102.0 litres | $99.45 |
How much does sharing a car cut the cost per person?
One trip with a fixed total cost of $124.31, split among a rising number of people.
| People sharing | Cost per person | Fuel cost |
|---|---|---|
| 1 | $124.31 | $124.31 |
| 2 | $62.16 | $124.31 |
| 3 | $41.44 | $124.31 |
| 4 | $31.08 | $124.31 |
| 5 | $24.86 | $124.31 |
Questions
What consumption figure should I use?
Your own, worked out from recent fill-ups: litres put in divided by kilometres travelled, times 100. Manufacturer combined figures are measured under test conditions and most drivers do not match them, particularly with a loaded car, a roof box or sustained high-speed driving.
Does the calculator include tolls, parking or wear?
No, only fuel. Fuel is typically well under half the true cost of running a car once tyres, servicing, insurance and depreciation are counted. For reimbursement or a genuine cost comparison, a per-kilometre rate covering all of it is the better basis.
Why is the driving time shorter than the trip really takes?
Because it is time in motion only, distance divided by average speed. Fuel stops, meals and breaks are not included, and on a long drive they can easily add an hour or more. Lowering the average speed entered is a rough way to allow for them.
Does carrying more passengers use more fuel?
Slightly, since the car is heavier, but far less than the saving from splitting the cost. Extra weight mostly affects acceleration and hill climbing rather than steady cruising, so the total in the second table is close enough to unchanged.
To work out your own consumption figure from a fill-up, see the fuel consumption calculator. To split a regular commute between riders, see the carpool cost calculator.