Why Use This Calculator?
The window sticker's MPG is a lab estimate; your actual number depends on how you drive, tire pressure, and whether the AC runs all summer. This calculator computes your true MPG the honest way — miles driven divided by gallons pumped, fill to fill.
Then flip to trip planning: enter a road-trip distance, your MPG, and the local gas price for the real fuel budget. A 500-mile trip in a 30-mpg car at $3.50 is $58.33 — the number that decides whether flying is actually cheaper.
How It Works
- Fill the tank, reset the trip meter, drive normally, and refill.
- Enter the miles driven and the gallons it took to refill.
- Use your real MPG in the trip cost panel for accurate road-trip budgeting.
Frequently Asked Questions
How do I calculate my gas mileage?
Fill the tank completely, note the odometer, drive, then refill fully and divide miles driven by gallons pumped. One fill-to-fill cycle gives a solid reading; three averaged gives a reliable one.
What is a good MPG?
Modern cars: 30+ mpg combined is good, 40+ is excellent for gas engines; hybrids run 50+; full-size trucks often sit near 20. Compare against your own previous readings — trends matter more than absolutes.
How do I estimate the fuel cost of a trip?
Divide trip miles by your MPG to get gallons, then multiply by the price per gallon — the second panel above does it directly, so you can compare driving against flying honestly.
Tips & Things to Watch
- Always refill the same way (auto-stop first click) for consistent readings.
- Highway MPG beats city by 20–30% — calculate them separately if you drive both.
- Roof racks and higher speeds cut real MPG far more than most drivers expect.