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Road Trip Fuel Cost Calculator

Enter your trip distance, fuel economy, and fuel price to estimate cost.

Result

How it is calculated

Fuel needed is distance divided by efficiency, and cost is fuel times price: gallons = distance ÷ mpg, cost = gallons × price, cost_per_mile = cost ÷ distance. distance is in miles for the whole trip, mpg is miles per US gallon and price is the price of one US gallon in your currency. The tool does one leg: for a return journey, enter the round-trip distance. Distance and price may be zero but not negative; mpg must be above zero. Gallons are shown to two decimals and money is rounded to cents, so the cost per mile, a small number, shows only two decimals. Efficiency is treated as constant, whereas real mpg changes with speed, load and terrain.

Worked example

A 450-mile trip, a car averaging 28 mpg and fuel at 3.80 per gallon. Step 1: gallons needed = 450 ÷ 28 = 16.0714, shown as 16.07 gal. Step 2: fuel cost = 16.0714 × 3.80 = $61.07. Step 3: cost per mile = 61.07 ÷ 450 = about 0.1357, shown rounded as $0.14. For the drive back, double the distance to 900 miles and the total becomes about $122.14.

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Common mistakes

  • Entering kilometres or litres. The tool works in miles, US gallons and mpg; convert first, because 100 km is about 62 miles, not 100.
  • Using the car's best advertised mpg. Fully loaded, with a trailer, roof box or at motorway speeds, real mpg is lower, so the true cost is higher.
  • Forgetting the return leg. The distance field is the total you drive, not the one-way distance.
  • Mixing up litres per 100 km with mpg. A bigger mpg means less fuel, while a bigger L/100 km means more, so the numbers cannot be swapped.
  • Using a fuel price from home when the route crosses areas with different prices; use an average for the route.

About this calculator

Estimating what a road trip will cost in gas comes down to three numbers: how far you're driving, how efficiently your vehicle burns fuel, and the price at the pump. This calculator combines them with the straightforward formula fuel cost = (distance ÷ mpg) × price per gallon — distance divided by fuel economy gives gallons needed, multiplied by price gives total cost.

A 600-mile trip in a car averaging 30 mpg at $3.50 a gallon burns 20 gallons and costs $70. Doubling the distance or halving the mpg (say, towing a trailer) doubles the fuel bill in the same way.

Road trippers and commuters use this to budget a trip in advance, compare the fuel cost of driving versus flying, or judge how much a more fuel-efficient vehicle would actually save on a specific route.

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Comments (1)

  • Editorial team

    This tool works in miles, US gallons and mpg. For a car rated in litres per 100 km, divide 235.2 by that number to get US mpg, which is a quick bridge before you type anything in. To split the cost on a shared trip, divide the fuel cost by the number of people in the car. Would you like kilometres and litres supported directly? Tell us which units you drive in.

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