Work out what fuel will cost for a drive, and split it between passengers. US gasoline averaged $4.085/gal in the EIA survey for Aug 24, 2026 — so a 500-mile trip at 28 MPG burns about 17.9 gallons and costs roughly $72.95.
Distance, fuel economy and price into a total.
Formula: gallons = miles ÷ MPG; cost = gallons × price. Fuel only — no tolls, food, depreciation or maintenance. The IRS mileage rate of roughly 67¢/mile is the figure that includes all of those.
What the identical drive costs on each state's pump price.
EIA publishes weekly retail prices for these states only, not all fifty — see gas prices by state for the full ranked survey and gas tax by state for why the spread is so wide.
Divide the trip distance by your car's MPG to get gallons, then multiply by the price per gallon. A 500-mile drive in a car doing 28 MPG needs about 17.9 gallons; at $4.00 a gallon that is roughly $71 each way. Remember to double it for the return leg unless the distance you entered is already the round trip.
Use your real highway figure rather than the sticker number if you know it, since road trips run mostly at highway speed where most cars beat their combined rating. If you do not know it, the trip computer average after a long drive is a good guide. Loading the car with people and luggage, running the air conditioning, a roof box, or driving at 80 rather than 65 all cut fuel economy noticeably — a roof box alone can cost 10 to 15%.
No, and the gap is large — often more than a dollar a gallon between the cheapest and most expensive states. Most of the difference is tax: state fuel taxes range from about 9 cents to nearly 70 cents a gallon, on top of the 18.4-cent federal excise. California and the West Coast also require special low-emission fuel blends that cost more to produce, and are supplied by a relatively isolated refining market. Crossing a state line before filling up can genuinely be worth it.
No — this is fuel only. The IRS standard mileage rate, which is around 67 cents a mile, is a far higher figure because it also covers depreciation, insurance, maintenance and tyres. For deciding whether to drive or fly, or what to charge a passenger, fuel alone understates the true cost of the trip.