Fuel Cost Calculator

Fuel cost calculator for road trips, commutes, and shared travel

This fuel cost calculator estimates how much gas or petrol a journey will use and what that fuel will cost. Enter the one-way distance, your vehicle's fuel economy, the current fuel price, and whether you are returning by the same route. The result includes total fuel needed, trip gas cost, cost per mile or kilometer, and fuel cost per person. You can use it as a road trip gas calculator, a daily commute cost calculator, or a quick way to split petrol money with passengers.

Fuel cost formulas

For miles per US gallon:

Gallons used = trip miles ÷ MPG

Gas cost = gallons used × price per gallon

For metric fuel consumption:

Liters used = trip kilometers × (L/100 km ÷ 100)

Fuel cost = liters used × price per liter

Road trip fuel cost example

Suppose a road trip is 300 miles one way, your car averages 30 MPG, and gas costs $3.50 per gallon. A one-way journey needs 300 ÷ 30 = 10 gallons and costs $35. Select round trip and the calculator uses 600 miles, 20 gallons, and a total estimated gas cost of $70. With four people sharing, that is $17.50 per person before tolls, parking, food, or other travel expenses.

Metric example using liters per 100 km

For a 450 km trip in a car rated at 7.2 L/100 km, expected fuel use is 450 × 7.2 ÷ 100 = 32.4 liters. At 1.65 per liter, the estimated petrol cost is 53.46. The currency symbol shown is only formatting; the same calculation works for dollars, euros, pounds, or any other currency as long as the price and result use the same one.

MPG versus L/100 km

MPG measures distance traveled per unit of fuel, so a higher MPG means better fuel economy. Liters per 100 kilometers measures fuel consumed over a fixed distance, so a lower L/100 km figure is better. Do not enter an MPG number into the metric field: 35 MPG and 35 L/100 km describe very different levels of efficiency. Choose the unit system used by your dashboard or official vehicle rating.

Estimating monthly commute fuel cost

To estimate commuting expenses, use the distance for one workday as the trip distance and multiply the result by the number of commuting days in the month. Alternatively, enter the combined monthly mileage directly. Remember that a commute cost estimate based only on fuel does not include maintenance, tires, depreciation, insurance, parking, or road tolls. Cost per mile for owning a vehicle is therefore higher than fuel cost per mile alone.

Why actual gas mileage can differ

• Traffic and idling: stop-and-go driving uses fuel while covering little distance.
• Speed: sustained high speed usually increases aerodynamic drag and consumption.
• Weather and terrain: cold starts, headwinds, hills, snow, and wet roads can reduce efficiency.
• Vehicle load: passengers, luggage, roof boxes, and towing increase energy use.
• Maintenance: tire pressure, wheel alignment, oil, and engine condition affect real MPG.

For a conservative travel budget, use your measured average economy rather than the best manufacturer figure and add a small buffer for detours and price changes. If you need to compare the new fuel price with an old one, use the percentage increase calculator. To divide a complete restaurant or travel bill, including a gratuity, try the tip and bill split calculator.