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Fuel Cost Calculator — Trip Gas Cost by MPG

Plan any road trip in seconds. Enter your trip distance, your vehicle's fuel efficiency (MPG) and the fuel price per gallon, and this free fuel cost calculator works out exactly how many gallons you'll need, what the trip will cost, and what you pay per mile. Switch between one-way and round-trip, and compare your car with a second vehicle or an EV to see which is cheaper for the journey.

Current as of November 2026. The default fuel price is the AAA national average for regular gasoline: $4.01 per gallon as of November 9, 2026 (AAA, gasprices.aaa.com). Prices vary by state and station and change daily, so always edit the price to match your local pump price before you rely on the result.

Trip distance (miles): 300 mi

Vehicle fuel efficiency (MPG): 30 MPG

Fuel price per gallon ($): $4.01

Gallons needed

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Total fuel cost

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Cost per mile

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fuel cost for every mile driven

Total distance

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Compare with a second vehicle or an EV (optional)

Second vehicle MPG (or EV equivalent MPGe)

Second vehicle fuel / charging cost per gallon or per kWh ($)

Enter a second vehicle's MPG and fuel price above to see which one is cheaper for this trip.

Worked example

Trip: 300 miles • Fuel efficiency: 30 MPG • Fuel price: $3.50 per gallon (one-way)

Gallons needed = 300 miles ÷ 30 MPG = 10 gallons
Total fuel cost = 10 gallons × $3.50 = $35.00
Cost per mile = $35.00 ÷ 300 miles = $0.117 per mile (about 12 cents a mile)

Try it yourself: set the sliders to 300 miles, 30 MPG and $3.50 per gallon and the calculator will show the same $35.00 result.

How It Works

This calculator uses three simple formulas. First, it divides your trip distance by your vehicle's miles per gallon (MPG) to find the gallons of fuel needed. Then it multiplies those gallons by the fuel price per gallon to get your total fuel cost. Finally, it divides the total cost by the distance to give your cost per mile. Choose "Round trip" and the distance is doubled before the same maths runs. The comparison box repeats the calculation for a second vehicle or an EV (using its MPGe and charging cost) and shows how much you would save or spend extra on the same trip.

Formulas: Gallons = Distance ÷ MPG • Total cost = Gallons × Price per gallon • Cost per mile = Total cost ÷ Distance

Frequently Asked Questions

How do I calculate fuel cost for a road trip?Divide the trip distance in miles by your car's MPG to get gallons needed, then multiply by the price per gallon. For example, 300 miles at 30 MPG uses 10 gallons; at $3.50 a gallon that costs $35.00.

What is a good MPG for a car in 2026?Most petrol cars average around 25–35 MPG, hybrids often reach 40–55 MPG, and many EVs are rated at 100+ MPGe. Check your owner's manual or fueleconomy.gov for your exact model.

How much does gas cost per mile?Divide the fuel price per gallon by your MPG. At $4.01 a gallon and 30 MPG, that's about $0.134 per mile. A more efficient car or cheaper fuel lowers your cost per mile.

How do I work out the cost of a round trip?Double the one-way distance first, then run the same calculation. This calculator has a round-trip button that does the doubling for you automatically.

Can I compare my car with an EV?Yes. Enter the EV's MPGe and your charging cost per kWh (or per gallon-equivalent) in the comparison box and the tool shows both trip costs side by side, including how much you save.

Why is my actual fuel cost different from the estimate?Real-world MPG varies with traffic, speed, air conditioning, hills, tyre pressure and how much you carry. Treat the result as a close estimate and add a small buffer (5–10%) for long trips.

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Disclaimer: Results are estimates only. Fuel prices change daily and vary by location, and real-world fuel economy depends on driving conditions, vehicle condition and load. This tool is for planning purposes and is not financial advice.