Fuel Cost Calculator
Enter a distance, your fuel economy and the fuel price to see the fuel used and what the trip costs.
What this tool does
A fuel cost calculator works out how much fuel a trip uses and what it costs. Enter the distance, your car’s fuel economy in the unit you know it in, and the price of fuel. It shows the fuel needed, the total cost, and the cost per kilometre and per mile.
Converts your fuel economy to litres per 100 km whatever unit you give it, then works out the litres needed for the distance and multiplies by the fuel price.
Shows the fuel used in litres, US gallons and UK gallons, and the cost per kilometre and per mile.
How to use it
- Choose a currency symbol if you want one.
- Enter the distance and choose kilometres or miles.
- Enter your fuel economy and choose its unit.
- Enter the fuel price and choose per litre or per gallon.
- Read the trip cost and fuel used.
Why use a fuel cost calculator
Accepts fuel economy in litres per 100 km, km per litre, US miles per gallon or UK miles per gallon, which is how people actually know their car. Fuel economy is quoted in different units in different countries - L/100 km in Europe, mpg in the US and UK - and US and UK gallons are different sizes. A calculator that handles all of them removes the most common error.
Why we built it
We built this to accept fuel economy in litres per 100 km, km per litre, US mpg or UK mpg, because people quote it in whichever way their car's dashboard does. The fuel economy converter shows all four at once, and the speed distance time calculator estimates how long the trip takes.
Related tools worth a look: the Tip Calculator and the Unit Price Calculator.
For a neighbouring job there is also the EV Charging Cost Calculator and the MPG Calculator.
Who this tool is for
- Drivers planning a road trip budget
- Commuters comparing car and train costs
- Anyone converting fuel economy between mpg and litres per 100 km
When to use it
- Budgeting a road trip or a commute.
- Splitting fuel costs with passengers.
- Comparing two cars’ running costs.
- Claiming mileage costs.
How it is calculated
Litres used = distance in km × L/100 km ÷ 100. Cost = litres × price per litre. Other units are converted first: km per litre = 100 ÷ economy; US mpg = 235.215 ÷ economy; UK mpg = 282.481 ÷ economy.
Worked example: 400 km at 7.5 L/100 km uses 30 litres, which at 1.85 per litre costs 55.50.
A UK gallon is 4.546 litres and a US gallon is 3.785 litres, so the same mpg figure means a different efficiency in each.
What you enter, and what you get back
| Item | Details |
|---|---|
| Distance and unit | The trip length in kilometres or miles. |
| Fuel economy and unit | L/100 km, km/L, US mpg or UK mpg. |
| Fuel price and unit | Per litre, US gallon or UK gallon. |
| Result | Trip cost, fuel used, cost per km and per mile. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| Cost much lower than expected | mpg was entered but L/100 km was selected. | Match the unit to your figure. |
| Different from my car’s computer | Real consumption varies with speed, load and traffic. | Use a real-world figure for your car. |
| US and UK mpg confusion | The gallons are different sizes. | Choose the right gallon. |
A worked example
These are the values the calculator opens with, so you can see exactly what it does with them. Change any value on the page and the result updates; the figures below come from the same calculation.
| Input | Value |
|---|---|
| Currency symbol | $ (dollar) |
| Distance | 400 |
| Distance unit | kilometres |
| Fuel economy | 7.5 |
| Economy unit | L per 100 km |
| Fuel price | 1.85 |
| Price is per | litre |
With those inputs, the calculator returns:
- Fuel cost for the trip: $55.50
- Fuel used: 30.0 litres (7.9 US gal, 6.6 UK gal)
- Cost per km: $0.14
- Cost per mile: $0.22
- Economy as L/100 km: 7.50
Rates and figures on this page
Figures checked on 16 October 2026. For reference, the AAA national average for regular petrol in the United States was about $4.41 per US gallon on 1 October 2026, which is about $1.17 per litre. Fuel prices change daily and differ by region, so use the price on your pump or receipt. The default price per litre of 1.85 is an example in your own currency.
Switch "Price is per" to match how your fuel is priced: litre, US gallon or UK gallon.
Assumptions and limitations
- Uses a single average economy for the whole trip.
- Does not include tolls, parking or wear.
- Real consumption varies with conditions.
- Round trips need the total distance entered.
Frequently asked questions
How do I calculate fuel cost for a trip?
Divide the distance by your fuel economy to find the fuel used, then multiply by the fuel price. This calculator handles the unit conversions.
What is the average fuel price?
Fuel prices vary by country, region and fuel type. In the United States, regular petrol averaged about $4.41 per US gallon in October 2026. Check a local fuel price tracker for current figures in your area.
How can I reduce my fuel costs?
Drive smoothly, keep tyres inflated, remove unnecessary weight and roof racks, stick to speed limits, and combine short trips. Maintaining your car well and planning routes to avoid congestion also helps.
Is diesel cheaper than petrol?
Not necessarily. Diesel prices vary by country and tax regime. Diesel engines are generally more fuel-efficient, so the cost per kilometre can be lower even if the per-litre price is higher.
How does driving style affect fuel cost?
Hard acceleration, high speeds and heavy braking can increase fuel consumption by 20% to 40% compared with smooth, steady driving. Gentle driving is the single cheapest way to cut fuel costs.
What is the most fuel-efficient speed?
Most cars are most fuel-efficient at 50 to 80 km/h (30 to 50 mph) in the highest gear. Fuel consumption rises sharply at higher speeds due to air resistance, which increases with the square of speed.