Estimating the fuel cost of a trip
Pricing a drive comes down to one chain of arithmetic. First find how much fuel the trip needs by dividing the distance by your vehicle’s fuel economy in miles per gallon. Then multiply those gallons by the price per gallon to get the trip cost. A 300-mile drive in a 30-mpg car burns 10 gallons, so at $3.50 a gallon it costs about $35. The numbers you enter are one-way unless you say otherwise, so for a round trip either double the distance or double the result — and remember this is fuel alone, not tolls, parking, or wear on the car. When you are also budgeting for the vehicle itself, ourauto loan calculatorhelps with the monthly payment side of ownership.
Worked example
Take a 300-mile drive in a car that does 30 mpg, with fuel at $3.50 a gallon. Here is the whole chain of arithmetic:
| Step | Amount |
|---|---|
| Trip distance | 300 mi |
| ÷ Fuel economy | 30 mpg |
| = Fuel neededdistance divided by miles per gallon | 10 gal |
| × Price per gallon | $3.50 |
| = Trip cost$0.12 per mile — double it for a round trip | $35.00 |
Computed with this calculator's default settings — open the tool above and you'll see the same numbers, then plug in your own trip.
Cost per mile and why it matters
The single most useful number here is the cost per mile — the trip cost divided by the distance. Because it does not depend on how far you drive, it puts very different trips and vehicles on the same footing. Use it to compare two cars before you buy, to weigh a long highway route against a shorter city one, or to see what a daily commute genuinely costs once you multiply by the miles you cover each year. Fuel is only one slice of the total cost of getting around; to see how it fits alongside rent, groceries, and the rest of a budget, ourcost of living calculatorgives the wider picture.
Metric units and electric vehicles
This tool works in US units — miles, gallons, and miles per gallon — so metric figures need converting first. Turn kilometres into miles by dividing by 1.609, litres into gallons by dividing by 3.785, and a price per litre into a price per gallon by multiplying by 3.785. A litres-per-100km economy rating becomes mpg with the formula 235.2 divided by that rating. Electric vehicles work on the same logic but a different unit: instead of gallons you measure kilowatt-hours per mile, and instead of a pump price you use your electricity rate, which gives an EV cost per mile you can hold up against a gasoline car.
Frequently asked questions
How do I work out the fuel cost of a trip?
Divide the trip distance by your vehicle’s fuel economy to find how many gallons you will burn, then multiply that by the price per gallon. For example, a 300-mile trip in a car that does 30 mpg uses 10 gallons, so at $3.50 a gallon the fuel cost is $35. The calculator does this for you and also reports the cost per mile.
What is cost per mile and why does it matter?
Cost per mile is the trip’s fuel cost divided by its distance — the price of moving your vehicle one mile. It matters because it strips away trip length and lets you compare fairly: a cheaper-to-run car, two competing routes, or the daily price of a commute. Multiply it by your annual mileage and you get a quick estimate of what driving really costs you each year.
Is the result one-way or round-trip?
The figures are for the distance you enter, which is normally one-way. If you are pricing a there-and-back journey, either enter the full round-trip distance or simply double the trip cost and fuel needed. The cost per mile stays the same either way, since it does not depend on how far you travel.
Does this work with metric units or kilometres per litre?
The calculator uses US units — miles, gallons, and miles per gallon. To use it with metric figures, convert first: kilometres to miles by dividing by 1.609, litres to gallons by dividing by 3.785, and a price per litre to a price per gallon by multiplying by 3.785. A litres-per-100km rating can be turned into mpg with the conversion 235.2 divided by the litres-per-100km value.
Can I use this for an electric vehicle?
Not directly, because an EV is charged with electricity rather than fuelled by the gallon. The idea still carries over, though: work out your energy use per mile in kilowatt-hours and multiply by your electricity rate to get a cost per mile you can compare against a gasoline car. For appliance-style energy costs, an electricity cost calculator is the better tool.
Disclaimer: This calculator is foreducation and illustration only. It estimates fuel cost from the distance, fuel economy, and price you enter and ignores tolls, parking, maintenance, and other costs of driving. Real-world fuel use varies with traffic, terrain, weather, and driving style. Nothing here is financial advice.