Fuel cost calculator for any trip
Estimate the fuel cost of a drive in MPG or L/100km, split it between passengers, add the return leg, and compare two vehicles on the same journey.
- Runs in your browser
- Nothing you enter is sent
- Free, no account
Doubles the distance so you see the there-and-back cost.
Optional — set it to see the weekly, monthly and annual bill for a commute.
Same trip, same fuel price, different economy — see which car to take.
- Total distance driven
- 640 miles
- Economy in L/100 km
- 7.35
- Fuel needed
- 75.71 L · 20 US gal · 16.65 imp gal
- Price per litre
- $0.91
- One-way cost
- $34.50
- Round-trip cost
- $69.00
distance = 1,029.98 km economy = 7.35 L per 100 km fuel = 1,029.98 × 7.35 ÷ 100 = 75.71 L cost = 75.71 L × $0.91/L = $69.00
This is fuel only. Real trip cost also carries tyres, servicing, depreciation and tolls — the widely used all-in figures put those at roughly the same again as fuel for an average car.
How to work out the fuel cost of a trip
- Enter the one-way distance and choose miles or kilometres.
- Leave round trip on if you are coming back.
- Enter your car's fuel economy and pick the unit it is quoted in — US MPG, imperial MPG, litres per 100 km or km per litre.
- Enter the pump price and say whether it is per gallon or per litre.
- Optional: set how many people are sharing, how often you make the trip, and a second vehicle to compare against.
Everything is converted to litres and kilometres internally, so you can freely mix a US MPG rating with a price per litre without converting anything yourself.
The formulas
fuel used = distance × consumption ÷ 100 (distance in km, consumption in L/100 km)
cost = fuel used × price per litre
Or, if you think in MPG and gallons:
cost = distance ÷ MPG × price per gallon
A 320-mile drive in a 32 MPG car with fuel at $3.45 a gallon needs 10 gallons and costs $34.50 one way, $69.00 there and back, or $34.50 each if two people split it.
Converting between economy units
| From | To L/100 km | Example |
|---|---|---|
| US MPG | 235.215 ÷ MPG | 32 US MPG = 7.35 L/100 km |
| Imperial MPG | 282.481 ÷ MPG | 40 UK MPG = 7.06 L/100 km |
| km per litre | 100 ÷ km/L | 14 km/L = 7.14 L/100 km |
| L/100 km | unchanged | — |
The two MPG scales are not interchangeable. An imperial gallon is 4.546 litres against the US gallon's 3.785, so the same car is rated about 20% higher in UK MPG. A car advertised at 40 MPG in Britain is roughly 33 MPG in the United States — get the unit wrong and your trip cost is off by a fifth.
Typical trip costs
| Distance | 20 MPG at $3.45 | 30 MPG at $3.45 | 40 MPG at $3.45 | 50 MPG at $3.45 |
|---|---|---|---|---|
| 50 miles | $8.63 | $5.75 | $4.31 | $3.45 |
| 100 miles | $17.25 | $11.50 | $8.63 | $6.90 |
| 250 miles | $43.13 | $28.75 | $21.56 | $17.25 |
| 500 miles | $86.25 | $57.50 | $43.13 | $34.50 |
| 1,000 miles | $172.50 | $115.00 | $86.25 | $69.00 |
Notice how the saving flattens out. Going from 20 to 30 MPG saves $57.50 over a thousand miles; going from 40 to 50 saves only $17.25. Consumption, not economy, is what scales linearly with cost — which is exactly why the rest of the world quotes litres per 100 km.
Getting a realistic economy figure
Manufacturer ratings come from a standardised laboratory cycle. Real-world consumption is typically 10–20% worse, and the gap widens with:
- Cold weather — a short winter trip can use 20–30% more fuel because the engine never reaches operating temperature.
- Motorway speed — aerodynamic drag rises with the square of speed, so 80 mph can cost 15–20% more per mile than 65 mph.
- Roof boxes and bike racks — often 10–25% at motorway speeds even when empty.
- Under-inflated tyres, heavy loads and air conditioning — a few percent each, which adds up on a long drive.
The reliable method is to fill the tank, reset the trip meter, drive normally, then fill up again and divide the distance by the fuel added. Two or three tanks of that gives a number worth trusting.
What this calculator does not include
This is fuel only. The full cost of running a car also carries tyres, servicing, insurance, tax and depreciation, which for an average vehicle roughly double the per-mile figure. Business mileage rates published by tax authorities are built to cover all of it, which is why they sit far above the pure fuel cost. When you are comparing driving with a train ticket or a flight, the fuel number is the floor, not the answer.
Splitting the cost
Set the number of passengers and the per-person figure appears alongside the total. For a regular commute, add the trips per week and the calculator projects the weekly, monthly and annual bill — usually the number that makes the case for a carpool on its own.
Privacy
No route lookup, no map service, no location access. You supply the distance, and every calculation happens in your browser.
Questions
Which fuel economy units are supported?
US MPG, imperial (UK) MPG, litres per 100 km and kilometres per litre. Everything is converted to litres per 100 km internally, so you can mix a US MPG figure with a price per litre without doing any conversion yourself.
Why is UK MPG higher than US MPG for the same car?
An imperial gallon is 4.546 litres against the US gallon's 3.785, so the same car travels about 20% further on one imperial gallon. A car rated 40 US MPG is roughly 48 UK MPG — pick the right unit or the cost will be wrong by a fifth.
Should I use the manufacturer's MPG figure?
Use your own if you have it. Official figures come from a standardised test cycle and real-world consumption is typically 10–20% worse, more in cold weather, on short trips or with a roof box. Fill up, reset the trip meter and divide distance by fuel used for a true number.
Does this include the full cost of driving?
No — it is fuel only. Tyres, servicing, insurance and depreciation roughly double the real per-mile cost for an average car, which is worth remembering when you compare driving with a train ticket.