Before a road trip or a new commute, the fuel question deserves a real answer: how much gas will this drive actually burn, and what will it cost? This tool computes gallons, liters and dollars in one pass.
Updated August 15, 2026, after a fresh review, with updated visuals and links.
It also splits the cost per person for carpools and flips your MPG into the metric L/100km used by the rest of the planet.
The numbers behind the drive
Fuel needed is distance divided by economy: 300 miles at 30 MPG burns 10 gallons. At $3.60 a gallon that's $36 each way, $72 round trip.
MPG versus L/100km runs opposite directions: higher MPG is better, lower L/100km is better. The bridge is 235.21 divided by your MPG: 30 MPG equals 7.8 L/100km, 40 MPG equals 5.9.
Real-world economy sinks below the window sticker with highway speed, roof boxes, cold engines and mountain climbs: budgeting 10 to 15% above the official number keeps trip math honest.
Worth remembering
- Gas stations near highways run pricier: filling up in town before merging often saves several dollars per tank.
- Steady 65 mph beats alternating 75 and braking: aerodynamic drag climbs with the square of speed, which is why the last 10 mph is the most expensive.
Frequently asked
How do I find my real MPG?
Fill the tank, reset the trip meter, drive normally, refill and divide miles driven by gallons added. Two or three tanks averaged beats one heroic estimate.
How do I convert MPG to L/100km?
Divide 235.21 by your MPG: 30 MPG is 7.84 L/100km. The tool prints both every time.
