Road trip gas cost calculator
Enter the trip distance, your car's fuel economy and the local gas price. You get the fuel cost, the gallons needed, the number of fill-ups, and each person's share.
Don't know the distance? Use the route planner.
Check your car's rating at fueleconomy.gov.
Enter today's local price. See AAA or EIA for averages.
- Distance
- 500 mi
- Gallons
- 17.9
- Fill-ups (from ¼ tank)
- 1
- Per person
- $31.25
- Cost per mile
- $0.125
How speed changes your fuel bill
At highway speed, most of your engine's work goes into pushing air out of the way. Drag grows with the square of speed, while tyre rolling resistance stays roughly flat. Move the slider to see how much of the work each one takes, and what that does to your trip's fuel if nothing else changes.
Air drag is 74% of road load at 70 mph.
+24% road load vs 60 mph
That would make this trip's fuel about $77.68 instead of $62.50. The model is a simplified physics sketch of a typical sedan (drag area 0.7 m², 1,500 kg, rolling coefficient 0.010). Real engines have a sweet spot, and gearing, hills, wind and air-con all shift the numbers. The direction holds, though: the U.S. Department of Energy's fueleconomy.gov notes that fuel economy usually falls off quickly above about 50 mph.
A roof box or bikes on the roof make the drag bar grow at every speed. That's why fuel costs rise so much once you load up for a long trip.
Gas cost questions
How do I calculate gas cost for a road trip?
Divide the trip distance by your car’s miles per gallon to get gallons, then multiply by the price per gallon. For example, 500 miles ÷ 28 mpg = 17.9 gallons, and at $3.50 that’s about $62.50.
Should I use my car’s city or highway mpg?
For road trips, use the highway rating, then knock off 10–15% if you’ll be heavily loaded, climbing mountains or driving well above 65 mph. Check the ratings at fueleconomy.gov.
How do I split gas money fairly?
The simplest method is total fuel cost divided by the number of people. The calculator shows the per-person share. Tolls and parking can be added on top.
What about electric cars?
Use the same idea: miles ÷ miles per kWh × price per kWh. For example, enter 3.5 as “mpg” and your charging price per kWh as the “gas price”.