MPG (Miles Per Gallon): The standard U.S. measure of fuel economy. The 2024 U.S. fleet average is about 26 MPG for cars and light trucks combined. Higher is better — a vehicle getting 35+ MPG is considered fuel-efficient.
km/L and L/100 km: Common outside the U.S. L/100 km is the European and Canadian standard — lower numbers mean better efficiency. A typical compact car uses 6–8 L/100 km.
Cost Per Mile (or km): Useful for budgeting and comparing vehicles. If you are choosing between two cars, the one with the lower cost per mile will save money over time.
Annual Fuel Cost: A projection based on your fuel economy and annual distance. Helps you see the yearly financial impact of your driving habits and fuel prices.
How This Calculator Works
You enter distance driven and fuel consumed in your preferred units. The tool divides distance by fuel to get the primary efficiency number, then converts internally to miles and gallons so it can display MPG, km/L, and L/100 km simultaneously. If you add a fuel price and annual mileage, it calculates cost per distance unit and projected yearly fuel spend.
Quick Questions
How do I calculate gas mileage between fill-ups?
Fill your tank completely, reset your trip odometer, drive normally until your next fill-up, then divide the miles driven by the gallons it took to refill. That gives you your real-world MPG for that tank.
Why is my actual MPG lower than the EPA estimate?
EPA testing uses standardized lab conditions. Real-world driving includes factors like cold starts, aggressive acceleration, highway vs. city mix, tire pressure, and cargo weight that can reduce MPG by 10–20% or more.
What is the difference between MPG and L/100 km?
MPG measures distance per unit of fuel (higher is better). L/100 km measures fuel consumed per unit of distance (lower is better). They are inversely related — you can convert between them using the formula L/100km = 235.215 ÷ MPG.
Does driving speed affect fuel economy?
Yes — most vehicles reach peak efficiency between 35–55 mph. Above 55 mph, aerodynamic drag increases rapidly, and fuel economy typically drops by 1–2% for every mph over 55. Cruise control on the highway helps maintain consistent efficiency.