🛣️ Fuel Cost Calculator

This fuel cost calculator estimates how much fuel a trip will burn and what it will cost, using just three numbers — distance, fuel efficiency, and fuel price. It works as both a metric fuel cost calculator (km, liters per 100km) and a US gas cost calculator (miles, MPG, price per gallon), switching the underlying formula automatically depending on which unit system you select, so it's useful anywhere in the world.

How It Works

In Metric mode, fuel needed is Distance (km) ÷ 100 × Efficiency (L/100km), then multiplied by the price per liter for the total cost. In US mode, fuel needed is Distance (miles) ÷ Efficiency (MPG), multiplied by the price per gallon. Checking "round trip" simply doubles the distance before either calculation runs, so you can enter the one-way distance and still get an accurate there-and-back total. The results panel also shows cost per mile or per km, letting you compare trips or vehicles on an even footing.

Why It Matters

Fuel is one of the largest variable costs of driving, and it's easy to underestimate on a long trip — especially when converting between L/100km and MPG, which move in opposite directions (lower is better for one, higher is better for the other). A quick fuel cost estimate helps with road trip budgeting, comparing vehicles before a purchase, or working out mileage reimbursement for work travel.

Tips for Accurate Results

• Use your vehicle's actual recent fuel efficiency (from the trip computer or a fill-up log) rather than the factory-rated figure, which is often optimistic.
• Double-check whether your fuel efficiency figure is L/100km or MPG before switching unit systems — entering the wrong one will give a badly skewed result.
• Update the fuel price field before longer trips, since prices can vary significantly by region and change frequently.
• Use the round-trip checkbox instead of manually doubling the distance yourself to avoid an easy arithmetic mistake.