Gas Mileage Calculator
Track your real fuel efficiency the way the EPA measures it: miles driven ÷ gallons used. Enter a tankful's worth of data and get MPG, the metric equivalent (L/100 km), your cost per mile, and an annual fuel bill projection at your local pump price.
Your Tank Data
How MPG Is Calculated
The formula is simple — and the two fill-ups make it accurate:
MPG = miles driven ÷ gallons to refill
L/100km = 235.215 ÷ MPG
Cost/mile = (price × gallons) ÷ miles
Fill the tank, zero the trip odometer, drive normally, and refill. The second fill's gallons — not the pump's estimate — are what the odometer distance actually consumed. The 235.215 constant converts US gallons and miles into the metric liters-per-100-km standard used across Canada, Europe, and much of the world.
Typical Fuel Costs by Vehicle Type
| Vehicle | Cost / Mile @$3.80 | L/100km | 12,000 mi / year |
|---|
At $3.80/gal. Real-world MPG varies with driving style, load, weather, and maintenance — EPA numbers are optimistic by roughly 10-15%.
How to Use This Calculator (3 Steps)
Case Study
Frequently Asked Questions
How do I calculate my gas mileage (MPG)?
Miles driven ÷ gallons to refill. Reset the trip odometer at each fill-up for accuracy.
How much does it cost to drive per mile?
Fuel price ÷ MPG. At $3.80/gal and 25 MPG that's $0.152 per mile.
What's the formula for liters per 100 km?
235.215 ÷ MPG. 25 MPG = 9.4 L/100km.
What is good MPG?
Sedans and hybrids 30-45 MPG highway; trucks/SUVs 20-25 MPG is typical.
How can I improve gas mileage?
Proper tire pressure, smooth driving (15-30% gain), steady highway speed, remove roof racks, keep up maintenance.