Gas Mileage Calculator
Fuel Efficiency Calculator
Fuel Efficiency
Ready for Calculation
Enter the distance traveled and fuel used to calculate your fuel efficiency.
Understanding Fuel Efficiency
Fuel efficiency describes how far your vehicle travels per unit of fuel. In the US it's expressed as miles per gallon (MPG) — higher is better. Most of the world uses liters per 100 kilometers (L/100km) — where lower is better — since it more directly reflects fuel consumed per trip.
MPG vs. L/100km
These two measures move in opposite directions: a higher MPG means better efficiency, while a lower L/100km means better efficiency. Converting between them is not a simple linear scale.
Track Over Time
Recording your mileage and fuel used at every fill-up over several tanks gives a far more reliable efficiency figure than any single tank, which can be skewed by short trips or weather.
What Affects Your Mileage?
Driving style, terrain, tire pressure, vehicle load, and even outside temperature all influence real-world fuel economy. Aggressive acceleration and heavy braking are among the biggest efficiency killers in city driving.
Cold Weather Penalty
Short trips in cold weather can reduce fuel economy by 15-20% because the engine never reaches its optimal operating temperature.
Key Takeaways
- Fill-to-Fill Method: Reset your trip odometer at a full tank and calculate MPG at the next full fill-up for the most accurate reading.
- Different From Reimbursement: This tool measures fuel efficiency, not tax or business mileage reimbursement — see our dedicated Mileage Calculator for that.
- Cost Awareness: Adding a fuel price lets you see your real cost per mile or kilometer, useful for budgeting or comparing vehicles.