How to Estimate Road Trip Fuel Costs
Distance, real-world MPG and fuel price — plus the speed and cargo factors that move the number.
3 min read
Step by step
- Fuel needed = trip distance ÷ your vehicle's real-world MPG.
- Multiply gallons by the fuel price for the trip cost.
- Metric: consumption in L/100km × distance ÷ 100.
- Add a 10% buffer for detours, traffic and headwinds.
Key takeaway: Use your real MPG, not the sticker figure.
The core calculation
Fuel needed = distance ÷ fuel economy. A 600-mile trip in a car rated 30 MPG uses 20 gallons; at $3.60 per gallon the trip costs $72. In metric, consumption is given per 100 km: 8 L/100 km over 950 km uses 76 litres.
Use your real-world economy, not the sticker figure — highway driving usually beats the combined rating, city driving and roof boxes fall short of it.
What moves the number
Speed is the biggest lever: aerodynamic drag rises with the square of speed, and most cars burn 15–25% more fuel at 80 mph than at 65 mph. Cargo weight, tire pressure, air conditioning and mountain routes all add a few percent each.
Add a 10% buffer to any estimate for detours, traffic and headwinds.
Comparing vehicles and routes
The calculator makes trade-offs concrete: taking the 30 MPG car instead of the 18 MPG SUV on a 1,200-mile round trip saves about $96 at $3.60/gal — often more than a toll-free detour costs in time.
For electric vehicles the same structure applies with kWh and charging prices; fast-charging on the road typically costs two to three times home rates.
Do it automatically
Trip fuel cost from distance, MPG or L/100km and fuel price.
Open the Fuel Cost Calculator