Gas Cost Calculator
Enter your trip distance, vehicle fuel efficiency, and current gas price to find the total fuel cost and gallons used for your journey. Great for road trips, commute budgeting, and comparing the cost of driving different routes.
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Formula
Cost = (Distance ÷ MPG) × Price per Gallon
Dividing distance by fuel efficiency gives the number of gallons consumed. Multiplying gallons by the per-gallon price gives the total fuel cost. All three variables have a direct effect: longer distance, lower MPG, or higher price each raise the total cost proportionally.
How to use the Gas Cost Calculator
- 1
Enter your distance (miles)
- 2
Enter your fuel efficiency (mpg)
- 3
Enter your gas price ($ per gallon)
- 4
Read your results instantly
Results update in real time as you type.
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Finding Your Vehicle's MPG
Your car's official MPG is on the window sticker or at fueleconomy.gov. Real-world MPG often differs from EPA estimates — highway driving typically meets or exceeds the rating, while city driving and idling reduce it. To measure your actual MPG, fill the tank completely, drive normally until near-empty, refill, and divide the miles driven by gallons added. Enter that real-world figure for the most accurate cost estimate.
Round-Trip Costs
To calculate a round trip, simply double the one-way distance before entering it. Alternatively, compute the one-way cost and multiply the result by 2. If the return route has a different distance (e.g., taking a detour), run the calculator twice and add the results. Many road-trippers budget 10-15% extra for detours, slow traffic, and extra idling.
Tips & Insights
Compare Vehicles
Run the calculator twice with different MPG values to see the dollar difference between a fuel-efficient car and a gas-guzzler for the same trip.
Account for City vs. Highway Mix
If your trip is 40% city and 60% highway, blend the two MPG ratings accordingly before entering a single value.
Gas Prices Vary by Route
Gas is cheaper in rural areas and some states. If you will pass through lower-price zones, average the prices along your route for a more accurate estimate.
Worked Examples
100-Mile Day Trip
$12.50 fuel cost, 3.57 gallons.
500-Mile Road Trip
$62.50 fuel cost, 17.86 gallons.
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Frequently Asked Questions
Where can I find current gas prices?
GasBuddy.com and AAA's gas price map show real-time prices by ZIP code and state. Google also shows local prices when you search 'gas price near me.'
How do I find my car's MPG?
Check fueleconomy.gov, your owner's manual, or calculate it yourself: fill up, drive, refill, and divide miles driven by gallons added.
Does speed affect fuel efficiency?
Yes. Most vehicles are most efficient between 45 and 60 mph. Highway speeds above 70 mph can reduce MPG by 10-20%.
How do I calculate fuel cost in liters?
Convert distance to km, fuel efficiency to L/100km, and price to per-liter. Cost = (distance_km / 100) × L/100km × price_per_liter.
Can I use this for electric vehicles?
Not directly. EVs use kWh per 100 miles (or miles per kWh) rather than MPG. Use an electricity cost calculator and your EV's efficiency rating instead.
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