Road-Trip Fuel Cost Calculator
One-way miles, real MPG, today's pump price, and the honest ±5 MPG band so the budget doesn't fail at the first mountain.
"Real MPG" is 10–15% below the EPA sticker in the real world (A/C, hills, roof box, highway speed over 65). The reality band shows the worst honest case.
How the math works
- Gallons = miles × round ÷ MPG. Cost = gallons × pump price. Per-person = cost ÷ split.
- Reality band recomputes at MPG−5 (and MPG−10 for the full-load option), the mountain-roof-box-A/C case every budget forgets.
- Stops = gallons ÷ 15 usable per tank (75% of a ~20 gal tank, range safety), plan them near cheap corridors; interstate fuel runs 40¢+ above off-exit pricing.
- Flight comparison is fuel-cost-only for a fair shape; add hotel/luggage/ground time for the real decision.
How much gas for a 700 mile round trip?
At 31 MPG and $3.55/gal: ~$80. At 26 MPG (A/C, hills, speed): ~$96. Split three ways it's a $27–32 round-trip fuel ticket per person, cheaper than two airline tickets, which is the comparison the row shows.
Why is my real MPG lower than the sticker?
The EPA cycle tests at 55–65 mph, no A/C, empty car. Highway 75 mph, A/C on, roof box, and four people is worth 4–7 MPG off the sticker in most sedans, that's the reality band, not pessimism.
When do fuel costs beat flying?
Under ~500 miles one way for 2+ travelers, flying usually loses on total cost (fuel + parking + bag fees). Above ~700 miles the flight + a rental car starts winning, the compare row frames the fuel side.