How to calculate gas cost for a road trip
- Enter the trip distance in miles (tick return trip for a round trip).
- Enter your car's fuel economy in miles per gallon.
- Enter the gas price per gallon and the number of people sharing the cost.
- Read the total gas cost, the cost per person and the cost per mile.
How the gas cost is calculated
Gallons used = miles ÷ mpg, and cost = gallons × price per gallon. A 250-mile trip in a car that gets 30 mpg uses 8.3 gallons; at $3.50 a gallon that is $29.17, or $14.58 each for two people. The cost per mile, here about 12 cents, is handy for comparing cars or planning regular commutes.
Highway mpg is usually better than the combined rating, but speed matters: above about 55–60 mph, fuel economy drops quickly, and driving at 75 mph can use about 15% more gas than at 65 mph. Roof boxes, heavy loads, under-inflated tyres and air conditioning also reduce mpg. For electric cars, switch to Electric and use kWh. The calculator runs in your browser.
FAQ
How do I find my car's mpg?
Check the trip computer, or fill the tank, reset the trip meter, and divide miles driven by gallons at the next fill-up.
How much gas does a 500-mile trip use?
At 25 mpg, 20 gallons; at 35 mpg, about 14.3 gallons.
Should I include tolls?
This calculator covers gas only; add tolls and parking separately.