Fuel Cost Calculator

What this calculator does

The Fuel Cost Calculator estimates how much fuel a trip will use and what that fuel will cost. It combines three inputs: the distance you plan to drive, the fuel efficiency of the vehicle, and the price of fuel. The result includes the gallons or liters consumed, the total trip cost, and the cost per mile and per kilometer.

The calculator accepts both US and metric units, so you can mix a distance in kilometers with efficiency in miles per gallon or a price per liter. Every input is converted to a common basis before the arithmetic is performed, which keeps the answer consistent across unit combinations.

How to use this calculator

1. Enter the trip distance and choose miles or kilometers.
2. Enter the fuel efficiency and choose mpg, L/100 km, km/L, or liters per mile.
3. Enter the fuel price and choose per gallon or per liter.
4. Click Calculate to see the fuel used, total cost, and unit costs.

For a round trip, double the one-way distance before entering it. The calculator does not add tolls, parking, maintenance, or depreciation; it reports fuel cost only.

Formula

Fuel used (gallons) = distance (miles) / fuel efficiency (mpg)
Trip cost = fuel used (gallons) x price per gallon
Cost per mile = trip cost / distance (miles)
Cost per kilometer = trip cost / distance (kilometers)

Unit conversions use 1 mile = 1.609344 kilometers and 1 US gallon = 3.785411784 liters. To convert L/100 km to mpg, divide 235.214583 by the L/100 km value. To convert km/L to mpg, multiply by 2.352145833.

Default example

With 500 miles, 25 mpg, and $3.00 per gallon, the trip uses 20 gallons and costs $60.00. The cost is $0.12 per mile, or about $0.0746 per kilometer. The result table also shows what the same trip would cost at 5, 10, 20, 30, 40, 50, and 60 mpg, which makes it easy to compare vehicles or driving styles.

Assumptions and limitations

• The estimate assumes the stated fuel efficiency matches real-world driving. Cold weather, traffic, hills, air conditioning, cargo, and aggressive driving can reduce efficiency.
• Fuel prices vary by station, region, and time. The entered price is treated as a constant for the whole trip.
• The calculator does not model refueling stops, fuel tank capacity, or partial fills.
• Results are rounded for display. The underlying calculation keeps full floating-point precision.
• Fuel efficiency conversions use the US gallon, not the imperial gallon.

Frequently asked questions

Why is my actual fuel cost higher than the estimate?

The entered efficiency is usually an EPA or manufacturer figure measured under controlled conditions. Real driving often includes idling, short trips, temperature changes, and higher speeds, all of which lower efficiency. Using a realistic highway or combined mpg usually gives a closer estimate.

Can I use L/100 km instead of mpg?

Yes. Choose liters per 100 km as the efficiency unit and enter the vehicle's figure. The calculator converts it to mpg internally, then reports the fuel used and cost in the units you selected.

How do I calculate a round trip?

Double the one-way distance. For example, a 250-mile one-way trip becomes 500 miles. If you prefer, calculate each leg separately and add the costs.

Reference table

Trip distance examples

Source

Reference: Calculator.net - Fuel Cost Calculator. Unit conversion factors follow the international mile and the US liquid gallon.