How much does it cost to drive across the country?

Gas for three cross-country Interstates

There’s no single cross-country distance. The Federal Highway Administration lists the length of each Interstate, which gives three well-defined cross-country drives to compare. Your door-to-door route will be longer or shorter, and your map app gives the real miles.

Miles ÷ MPG × price, calculated with the trip gas cost engine. The route lengths are FHWA’s end-to-end Interstate lengths, which include sections shared with other Interstates.

A national average price is used for the whole drive. Real prices change from state to state, which the next sections show.

Reference: EIA: Gasoline and Diesel Fuel Update · FHWA: Route Log and Finder List, Table 1 (Main Routes)

Where you fill up changes the bill

A cross-country drive buys gas in many places. For the same week, EIA’s regional averages differed by more than $1.60 a gallon. Here is what the same 20 gallons, 500 miles at 25 MPG, cost at each area’s average.

EIA regional and state averages, all taxes included. California is a state average within the West Coast region.

If most of your miles are in one region, use that region’s average in the calculator, or type the prices you expect.

Reference: EIA: Gasoline and Diesel Fuel Update

I-80 priced where you’d actually buy the gas

Using one national price for the whole drive is a shortcut. FHWA lists I-80’s miles in each state, and EIA publishes an average for each region and for some states, so the crossing can be priced piece by piece.

Total: $536.87, the sum of the rows, compared with $517.94 at the U.S. average. Each row is its miles ÷ 25 MPG × its area’s price, rounded to the cent.

California and Ohio use their own EIA state averages. The other states use the average for the EIA region they fall in: Nevada “West Coast less California”, Pennsylvania and New Jersey Central Atlantic. Where exactly you fill up still moves the total.

Reference: EIA: Gasoline and Diesel Fuel Update · FHWA: Route Log and Finder List, Table 1 (Main Routes) · EIA: States and cities by PADD for retail motor gasoline

Moving one way, or driving back?

A one-way move pays for one crossing. If you’re driving back, the gas doubles: $1,035.88 for I-80 end to end and back at 25 MPG and $4.478 a gallon.

If you’re driving a rental truck or towing a trailer, use that vehicle’s own fuel economy, not your car’s rating, and if it takes diesel, type a diesel price in the calculator. The estimate changes in proportion.

Splitting the gas between drivers and passengers

The $517.94 I-80 crossing at 25 MPG divides like this, with the driver paying a share or not:

Shares rounded to the cent. A solo driver has no passengers to share with.

Decide how to split gas money fairly ↗

Your speed changes the MPG

In a model the Department of Energy publishes for a midsize gasoline car, fuel economy is 45 MPG at 55 mph, 38 MPG at 65 mph and 32 MPG at 75 mph. Over thousands of miles, the speed you hold changes the gas bill.

See what driving slower saves on a long drive ↗

Reference: DOE Alternative Fuels Data Center: Fuel economy at various driving speeds

What the gas figure leaves out

A cross-country trip takes several days of driving, so the budget also needs lodging, food, tolls and parking. Wear, maintenance and depreciation are real costs of the miles too, even though you don’t pay them at the pump.

Those depend on your route, stops and car, so this guide doesn’t put a number on them. Add the tolls you expect in the calculator’s tolls and parking field; list the rest separately.

Use the calculator with your numbers

The worked example below comes from the trip gas cost calculator’s engine: the I-80 crossing for two people. Enter your own route’s miles, your car’s MPG and the price where you’ll fill up.

Route length from FHWA; the car’s MPG is an example. Lodging, food, tolls and wear are not included.

Illustrative figures, not market averages. The underlying costs are calculated with the same engine as the tool; additional derived measures are labeled.

About this guide

Prepared by RealCostTools with AI-assisted research and drafting. Sources and calculations were checked September 27, 2026. Prices are EIA averages for the week of September 21, 2026; route lengths are FHWA’s. Every car and trip in this guide is an example.

Sources and calculation notes

• EIA: Gasoline and Diesel Fuel Update

  Regular gasoline retail prices for the week of September 21, 2026, released September 22, 2026: U.S. $4.478, West Coast $5.600, California $6.003, Rocky Mountain $4.510, Midwest $4.386, East Coast $4.285, Gulf Coast $3.972 a gallon, all taxes included. Checked September 27, 2026.

• FHWA: Route Log and Finder List, Table 1 (Main Routes)

  Interstate lengths as of December 31, 2025 (page updated March 10, 2026): I-80 2,891.59 miles, I-40 2,552.90 miles, I-10 2,457.62 miles. Checked September 27, 2026. Route lengths, not door-to-door trips.

• DOE Alternative Fuels Data Center: Fuel economy at various driving speeds

  Modeled fuel economy of a midsize conventional gasoline car: 45 MPG at 55 mph, 38 MPG at 65 mph and 32 MPG at 75 mph (Oak Ridge National Laboratory, Transportation Energy Data Book #39, Table 4.33; worksheet updated May 2021). Checked September 27, 2026.

• RealCostTools: trip gas cost methodology

  The formulas behind every amount in this guide.

• EIA: States and cities by PADD for retail motor gasoline

  EIA’s map of which states fall in each gasoline price region (Nevada in the West Coast region; Utah and Wyoming in Rocky Mountain; Nebraska, Iowa, Illinois and Indiana in the Midwest; Pennsylvania and New Jersey in Central Atlantic). Checked September 27, 2026.

Read the trip gas cost methodology for the model assumptions and excluded costs.

Published October 4, 2026. Sources checked September 27, 2026. Editorial policy · Corrections