How to use this fuel cost calculator
- Choose miles or kilometers and enter the one-way trip distance.
- Enter your vehicle's fuel economy in US mpg or L/100 km.
- Enter the fuel price per gallon or per litre.
- Select round trip if you're coming back the same way.
- Enter how many people are sharing the cost to see each person's share.
How it's calculated
With US units, the calculator first finds how many gallons the trip uses, then multiplies by the price: cost = distance ÷ mpg × price per gallon.
With metric units, fuel economy is stated as litres used per 100 km, so the formula becomes: cost = distance × L/100 km ÷ 100 × price per litre.
Choosing round trip doubles the distance before anything else is calculated, and the split divides the final cost by the number of people.
Example: you drive 280 miles each way, so the round trip is 560 miles. At 32 mpg, that uses 560 ÷ 32 = 17.5 gallons. With gas at $3.40 a gallon, the trip costs $59.50, or about $19.83 each for three people.
In metric, a 450 km drive in a car using 6.5 L/100 km burns 450 × 6.5 ÷ 100 = 29.25 litres. At $1.75 a litre, that's about $51.19.
Ways to spend less on fuel
- Use your real-world fuel economy. Fill the tank, reset the trip meter, and at the next fill-up divide the distance driven by the fuel you added.
- Ease off on the highway. Aerodynamic drag rises sharply with speed, so driving a little slower can save noticeably on a long trip.
- Check tire pressure before you leave. Underinflated tires increase rolling resistance and wear out faster.
- Take off roof racks and cargo boxes when you aren't using them.
- Compare fuel prices along your route. Stations right beside highway exits often charge more than those a short drive away.
- If your engine only requires regular fuel, paying for premium won't improve your fuel economy.
Good to know: US and UK mpg figures aren't the same. A US gallon is 3.785 litres and an imperial gallon is 4.546 litres, so the same car shows a higher mpg in UK figures. Enter US mpg here, or switch to L/100 km.
Frequently asked questions
How do I calculate gas cost for a road trip?
Divide the trip distance in miles by your car's mpg to get the gallons used, then multiply by the price per gallon. For a round trip, double the distance first. The calculator does this for you and can split the total between passengers.
How do I convert mpg to L/100 km?
Divide 235.2 by the US mpg figure. For example, 30 mpg is about 7.8 L/100 km. To convert back, divide 235.2 by the L/100 km figure. For UK (imperial) mpg, use 282.5 instead of 235.2.
Why does my real fuel cost differ from the estimate?
Speed, traffic, hills, air conditioning, cargo and cold weather all change fuel economy, and higher highway speeds usually cut it noticeably. Using the fuel economy you have measured yourself gives the most accurate result.