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Fuel Cost Calculator

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Estimate the total fuel cost for a trip based on distance, your vehicle's fuel efficiency, and the fuel price - in miles/gallons or km/liters.

Fuel Cost Calculator

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Estimated fuel cost
$36.96
Fuel needed
10.71 gal
Total distance
300 mi

Compare two vehicles

Using the same trip distance and fuel price above, compare fuel cost between two vehicles with different efficiency.

Vehicle A cost$36.96
Vehicle B cost$22.99
Difference$13.97 (Vehicle B cheaper)

The formula

Imperial: Fuel needed (gallons) = Distance (miles) / Efficiency (mpg) Metric: Fuel needed (liters) = (Efficiency (L/100km) / 100) x Distance (km) Fuel cost = Fuel needed x Price per unit Round trip: multiply distance by 2 before calculating fuel needed
Example

A 300-mile one-way trip at 28 mpg, with gas at $3.45/gallon: 300 / 28 = 10.71 gallons needed, for a cost of $36.96. The same trip round-trip (600 miles total) would cost roughly $73.93.

Step-by-step guide

  1. Choose your unit system - miles/gallons or kilometers/liters - and whether this is a one-way or round trip.
  2. Enter your trip distance, fuel efficiency, and current fuel price.
  3. Use the comparison section below to see the cost difference between two vehicles for the same trip - useful when deciding which car to take, or evaluating a potential new vehicle.

Why real-world mileage often differs from the sticker rating

EPA or manufacturer-rated fuel efficiency figures come from standardized lab testing conditions that rarely match everyday driving. City driving with frequent stops, cold weather, highway speeds above 65 mph, a loaded roof rack, or aggressive acceleration can all reduce real-world efficiency by 10-20% or more below the rated figure. For the most accurate cost estimate, track your own actual mileage over a few tanks (dividing miles driven by gallons used) rather than relying solely on the window sticker or manufacturer specification, especially if your typical driving conditions differ from standard test conditions.

Common mistakes

Using your car's advertised EPA fuel economy rating without adjustment - real-world mileage is often somewhat lower, especially in city driving, cold weather, or at highway speeds above the EPA test conditions.
Forgetting to select "round trip" when planning for the full journey - a one-way calculation understates true cost by half if you're actually driving there and back.
Mixing L/100km with mpg-style thinking - unlike mpg, a LOWER L/100km number means BETTER efficiency, which can confuse comparisons if you're used to the imperial convention where higher is better.

Frequently asked questions

Where can I find my car's actual fuel efficiency?

Track it yourself using our Gas Mileage Calculator - fill up, reset your trip odometer, and calculate your real mpg (or L/100km) the next time you fill up, which is often more accurate than the sticker rating for your specific driving.

Why does L/100km work backwards compared to mpg?

Mpg measures distance per unit of fuel (higher is better), while L/100km measures fuel per unit of distance (lower is better) - both describe the same underlying efficiency, just inverted, which is why a "good" number looks very different between the two systems.

Does this calculator account for traffic, idling, or air conditioning use?

Not directly - these factors reduce real-world efficiency below the rated figure. Using a slightly lower efficiency number than your car's official rating (or your own tracked average) helps account for typical driving conditions like this.

How does the vehicle comparison tool help when car shopping?

Enter your typical annual mileage as the "distance," and compare the fuel efficiency ratings of two vehicles you're considering - the resulting cost difference, projected over a year or the years you'd own the car, can be a meaningful factor alongside purchase price and other costs.

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