Fuel Cost Calculator

Road-trip fuel cost ties together distance, fuel economy, and pump price. In US mode, gallons needed = miles ÷ MPG, then cost = gallons × price per gallon. Metric mode uses liters = km × (L/100 km) ÷ 100, then cost = liters × price per liter. Toggle the unit switcher to match your dashboard and gas station signs.

Real-world MPG or L/100 km rarely matches the window sticker every mile. Highway cruising beats stop-and-go city traffic. Loaded trunks, roof boxes, cold weather, and aggressive acceleration all drag economy down. Use your trip computer’s long-term average if you track one, or EPA combined rating as a starting guess.

Default US example: 350 miles at 28 MPG burns 350 ÷ 28 = 12.5 gallons. At $3.65/gallon, that is about $45.63 one-way. Round-trip doubles fuel unless you refuel mid-route at different prices — this tool assumes one price for the whole leg.

Common mistakes include using city MPG for an interstate haul (or vice versa), forgetting that metric economy is inverse to MPG (lower L/100 km is better), and comparing diesel gallons to gasoline pricing without converting. EV road trips need a different kWh model entirely.

Carpool splits divide the fuel cost output by passengers — after calculating trip cost, divide by riders for each person's share; this tool does not split automatically.

Gas price apps show station-specific prices — update the price field when you know which exit you will use rather than a statewide average.

A 10% buffer on gallons accounts for detours and idling — multiply the gallons result by 1.1 mentally for conservative trip budgeting.

Limits: fuel only — no tolls, parking, wear, or lodging. Does not model elevation, headwinds, or partial refills at varying prices along the route.