Gas Cost Calculator for Trips
Enter the trip distance and your car's fuel economy, then choose a state to use this week's average regular gas price from the EIA (week of 11/09/26) — or type the price at your station.
How trip fuel cost is calculated
Gallons = miles ÷ MPG
Trip cost = gallons × price per gallon
Metric: liters = km × (L/100 km) ÷ 100
Example
A 300-mile drive in a car that gets 28 MPG uses 300 ÷ 28 = 10.7 gallons. At this week's U.S. average of $4.00 per gallon that costs about $42.80. Make it a round trip and split it between three friends and each person pays about $28.54.
Where the gas prices come from
State prices are the weekly average retail price of regular gasoline published by the U.S. Energy Information Administration. The EIA publishes separate prices for nine large states (California, Colorado, Florida, Massachusetts, Minnesota, New York, Ohio, Texas and Washington). For other states we use the EIA's regional average for that part of the country. See gas prices this week for the full table.
Ways to cut trip fuel cost
- Slow down. Fuel economy usually drops quickly above 50–60 mph.
- Check tire pressure. Under-inflated tires waste fuel.
- Remove roof racks and boxes when you don't need them.
- Fill up before toll roads and in lower-price states on long trips.
Frequently asked questions
How do I calculate gas cost for a trip?
Divide the distance by your car's miles per gallon to get gallons, then multiply by the price per gallon. 450 miles ÷ 30 MPG = 15 gallons; at $3.50 that is $52.50.
How much does it cost to drive 100 miles?
At 28 MPG and this week's U.S. average of $4.00 per gallon, 100 miles costs about $14.27.
Where does this week's gas price come from?
From the U.S. Energy Information Administration's weekly Gasoline and Diesel Fuel Update (regular gasoline). The current data is for the week of 11/09/26.
Should I use highway or combined MPG?
For a mostly highway road trip, the highway MPG (or a little below it at higher speeds) is more accurate. For mixed driving use the combined figure.
Sources
- U.S. Energy Information Administration — Gasoline and Diesel Fuel Update
- FuelEconomy.gov — Find your car's MPG