Fuel Cost Calculator
Calculate fuel costs and MPG
Fuel Cost Calculator tool
Trip Details
Vehicle Details
Vehicle Comparison
Fuel Cost Calculator: key facts
- What it does
- Calculate fuel costs and MPG
- Category
- Other Calculators
- Cost
- Free, with no account, sign-up, or install.
- Your data
- Runs entirely in your browser — the files and text you enter are never uploaded to a server.
- Last reviewed
- . Report an incorrect result.
About the Fuel Cost Calculator
Before a road trip or a daily commute, it helps to know what the fuel will actually cost. This calculator works it out from your distance, your vehicle's efficiency, and the price of fuel, and it can compare several vehicles to show which is cheapest to drive.
Travelers budget trips with it, commuters weigh the running cost of one car against another, and anyone deciding whether to drive or take another option puts a number on the journey. It works in both imperial (miles, gallons, MPG) and metric (kilometers, liters, L/100km) units, with a round-trip toggle so you do not have to double the distance yourself.
How to use it
- Choose imperial or metric units.
- Enter the distance, and tick "round trip" if you are returning.
- Enter your vehicle's fuel efficiency and the price of fuel.
- Read the total cost, fuel needed, and cost per mile or kilometer — and add vehicles to compare their running costs.
Distance, efficiency, price
The calculation divides distance by fuel efficiency to get the volume of fuel required, then multiplies by price. The tool also derives a cost per mile and a cost per kilometre, which are the figures worth remembering — once you know your per-mile cost, any journey can be estimated in your head.
Efficiency is the input that decides everything, and it is the one most people get wrong by using the manufacturer's figure. Official consumption numbers are measured under standardised test conditions and real-world results are routinely worse. Your own average, taken over several tanks, produces a far more useful answer.
The vehicle comparison lets you run the same trip against a second efficiency figure, which is the honest way to evaluate whether a more economical car pays for itself over the mileage you actually drive.
- The defaults — 250 miles at 25 mpg with fuel at $3.50 — need 10 gallons and cost $35.00.
- That works out at $0.140 a mile, or $0.087 per kilometre.
- The same journey in a 40 mpg car needs 6.25 gallons and costs $21.88 — over $13 saved on a single trip.
Why use this version
- It supports both imperial (MPG) and metric (L/100km) units with the correct conversions, so it works wherever you are.
- A vehicle-comparison feature ranks multiple cars by running cost and shows the savings between the cheapest and priciest.
- A round-trip toggle and a cost-per-distance figure give you the numbers that matter for budgeting a journey.
- It runs entirely in your browser with no sign-up.
What fuel does not cover
Fuel is the visible cost of driving and rarely the largest. Depreciation, insurance, tax, servicing, tyres, and parking together usually exceed it comfortably, which is why published per-mile running costs from motoring organisations come out well above any fuel-only figure. For deciding whether to drive or take the train, the fuel number understates the real comparison.
Efficiency itself is not a constant. It falls with high speeds, hard acceleration, short journeys from cold, heavy loads, roof boxes, under-inflated tyres, and air conditioning, and it varies between city and motorway driving by a wide margin. Cold weather reduces it noticeably.
Two notes on units, since fuel is measured inconsistently across the world. US and imperial gallons differ by about 20%, so an mpg figure is meaningless without knowing which. And litres per 100 km is an inverse measure — lower is better — so it cannot be compared with mpg by intuition; it has to be converted.
Frequently Asked Questions
How do I calculate the fuel cost of a trip?
Divide the distance by your fuel efficiency to find how much fuel you need, then multiply by the price per unit. The calculator does this in either unit system — for metric it uses the L/100km method instead of dividing.
What is the difference between MPG and L/100km?
MPG (miles per gallon) measures distance per unit of fuel, so higher is better. L/100km measures fuel per fixed distance, so lower is better. They run in opposite directions, which is why the calculator handles each with its own formula.
How does the vehicle comparison work?
Add each vehicle with its fuel efficiency, and the calculator computes the trip cost for all of them at the same distance and fuel price, then ranks them and shows how much you save by choosing the most efficient one.
Does this include tolls, parking, or wear and tear?
No — it estimates fuel cost only. The true cost of driving also includes tolls, parking, maintenance, and depreciation, so treat the result as the fuel portion of a trip rather than its total cost.
