Fuel planning
Estimate gas cost before the trip starts.
A fuel cost calculator turns miles, MPG, fuel price, and passenger count into a simple trip budget.
Last updated: August 27, 2026
The basic fuel cost formula
Fuel cost starts with distance. Divide miles by expected miles per gallon to estimate gallons needed. Then multiply gallons by the price per gallon. If the trip is round trip, double the one-way miles before calculating gallons.
Gallons needed = miles / MPG
Total fuel cost = gallons needed x price per gallon
Cost per person = total fuel cost / passengers
Pick a realistic MPG
The MPG shown on a dashboard, sticker, or past trip is an estimate. Highway driving may be more efficient than city driving. Fast speeds, heavy traffic, idling, hills, low tire pressure, roof racks, towing, air conditioning, and heavy cargo can reduce fuel economy.
For planning, it can help to run two estimates: one with your normal MPG and one with a lower MPG. The lower estimate gives a cushion for traffic, weather, and route changes.
Passenger split example
If a round trip is 300 miles, the vehicle gets 25 MPG, and gas costs $3.50 per gallon, the trip needs about 12 gallons. The estimated fuel cost is $42. If four people split it evenly, the fuel share is $10.50 per person.
That estimate does not include tolls, parking, maintenance, wear, or a driver's time. It is a fuel-only estimate, which is useful when the group only wants to split gas.
What to verify before driving
- Check whether the mileage is one way or round trip.
- Use a fuel price close to the area where you will refill.
- Use a realistic MPG for highway, city, towing, or loaded travel.
- Add a cushion if gas prices vary along the route.
- Keep tolls, parking, and maintenance separate from fuel-only splits.