How to work out the cost of a road trip
A road trip costs three things: fuel, which depends on distance, fuel economy and price; tolls and parking, which are fixed; and the car’s wear and tear, which many people forget.
The fuel math
Gallons = miles ÷ mpg. A 250-mile trip each way is 500 miles round trip. A car that gets 30 mpg burns 16.7 gallons; at $3.20 a gallon that is $53.33 of fuel. Add $20 of tolls and $40 of parking and the trip costs $113.33, or $37.78 for each of 3 people. Outside the U.S., use liters per 100 km: liters = km × L/100 km ÷ 100.
Wear and tear
Tires, oil, maintenance and depreciation add roughly 10 to 30 cents per mile for an ordinary car. When the car belongs to one of the travelers, including this cost makes the split fairer. The standard mileage rates published by tax authorities are higher because they also include insurance and financing.
Splitting the bill
Total cost barely changes with the number of passengers, so every extra person makes the trip cheaper for everyone. If people paid for different things along the way, use the expense splitter to settle up with the fewest transfers.
Diesel, CNG or electric
Tick the fuels you want to compare. An EV that uses 30 kWh per 100 miles needs 150 kWh for the 500-mile trip. Charging half at home ($0.17 per kWh) and half at public fast chargers ($0.45), the energy costs $46.50 and the whole trip $106.50, $6.83 less than with gasoline; charging only at home, the energy would cost just $25.50. A diesel pickup at 24 mpg and $3.75 a gallon would spend $78.13 on fuel. CNG is sold by the gasoline gallon equivalent (GGE): at 28 mi/GGE and $2.95, the fuel would cost $52.68.
Suggested prices are rough averages: check the pump, your electric bill and the charger before deciding.