Fuel Cost Calculator · Practical guide
How Much Will Gas Cost for My Road Trip?
Trip distance divided by your MPG, times the price per gallon — a 300-mile trip at 25 MPG costs about $42.
At a glance
The Short Answer
Gas cost for a road trip is distance ÷ MPG × price per gallon. A 300-mile trip in a car that gets 25 MPG with gas at $3.50 uses 12 gallons and costs about $42.00. Enter your own distance, efficiency, and local price in the calculator above for your exact figure.
Interactive tool
Fuel Cost Calculator
Enter your own values, then compare the result with the examples below.
Fuel Cost Results
A Worked Example
Say you are driving 300 miles each way to visit family:
- Round-trip distance: 600 miles
- Your car: 25 MPG highway
- Gas price along the route: $3.50 per gallon
Fuel needed: 600 ÷ 25 = 24 gallons. Total cost: 24 × $3.50 = $84.00, or $0.14 per mile.
Budget a Buffer for Real-World Driving
Your actual mileage will differ from the EPA figure. Add 10-15% to the estimate if your trip includes city driving, heavy cargo, a roof box, mountain grades, or winter weather — all of which cut MPG. For the $84 example, budgeting $95 covers the realistic range.
MPG and L/100km Both Work
If your car or route is measured in metric units, switch the calculator to L/100km mode and enter kilometers and the price per liter. Remember that the two efficiency scales run opposite directions: higher MPG is better, while lower L/100km is better.
Quick Ways to Cut Trip Fuel Cost
- Drive 65 mph instead of 75 — highway fuel economy drops noticeably above 65.
- Check tire pressure before leaving; underinflated tires can cost a few percent of MPG.
- Fill up away from highway exits, where prices are often 10-20 cents higher per gallon.
Frequently Asked Questions
How do I estimate gas for a trip with multiple stops?
Add up the total miles across all legs — your map app's full route distance works — and enter it as a single trip distance. Stops barely affect fuel use compared with total miles.
Should I use city or highway MPG?
Use the figure closest to your actual driving mix. For a mostly highway trip, use your highway MPG; for mixed driving, the combined rating is a better estimate.
Does this work for diesel vehicles?
Yes. The math is identical — just enter the diesel price per gallon instead of the gasoline price.
How do I split the cost with friends?
Divide the total cost by the number of people sharing. On the $84 round trip above, four passengers would pay $21 each.