Gallons burned times the pump price
Distance divided by miles per gallon gives the gallons the trip needs; multiply that by the price per gallon for the total. Round-trip mileage counts, not one-way. A quick sanity check for a typical car: miles ÷ 20 × the gas price lands close.
What common trips cost, at about $3.80 a gallon
| Distance | 25 mpg | 30 mpg | 40 mpg (hybrid) |
|---|---|---|---|
| 100 mi | $15.20 | $12.67 | $9.50 |
| 300 mi | $45.60 | $38.00 | $28.50 |
| 500 mi | $76.00 | $63.33 | $47.50 |
| 1,000 mi | $152.00 | $126.67 | $95.00 |
Scale the figures to your own price: at $4.50 a gallon everything here rises about 18 percent, and at $3.00 it drops about 21 percent.
The two things that throw the estimate off
- Optimistic mpg. The window-sticker number assumes ideal conditions. Highway pace, a loaded car, roof boxes, cold starts and AC all pull the real figure below it, so a trip can cost more than the math suggests.
- Price varies by the mile. Gas is cheaper off the interstate than at highway-exit stations, and it swings by state. For a long trip, plan a fill-up or two away from the busiest exits.
Common questions
How do I estimate fuel cost for a road trip?
Divide the trip distance by your car's miles per gallon to get the gallons you'll burn, then multiply by the price per gallon. A 600-mile trip in a 30 mpg car at $3.80 is 20 gallons, or about $76.
Should I use the EPA mpg number for my car?
Knock it down first. EPA figures come from ideal test conditions, so real highway driving is often 15 to 25 percent lower, and more in cold weather, hills, or with the AC running. Better still, use your own average from a few fill-ups.
Does driving faster use more fuel on a road trip?
Yes. Above about 50 mph, every extra 5 mph cuts mpg by roughly 5 percent. Cruising at 70 instead of 55 can burn around 20 percent more fuel over the same distance.
