Calculate fuel economy, MPG, L/100km, and trip cost
Our Gas Mileage Calculator computes your vehicle's fuel economy in multiple units simultaneously — MPG (miles per gallon), L/100km (liters per 100 kilometers), and km/L (kilometers per liter). It also estimates trip fuel cost based on your local fuel prices.
Understanding your vehicle's fuel economy helps you budget for trips, evaluate the efficiency of different vehicles, and identify changes in your car's performance that may signal maintenance issues. The calculator supports both US and metric units with a single toggle.
MPG (miles per gallon) measures how many miles you can travel on one gallon of fuel — higher is better. L/100km (liters per 100 kilometers) measures how many liters of fuel are needed to travel 100 kilometers — lower is better. MPG is common in the US and UK, while L/100km is standard in most other countries.
The conversion formula is: L/100km = 235.214 / MPG (US). For example, 30 MPG = 235.214 / 30 ≈ 7.84 L/100km. For UK (imperial) gallons, use 282.481 instead of 235.214.
The trip cost estimation is an approximation based on the fuel economy you entered or calculated and the fuel price you provide. Actual costs may vary due to driving conditions (city vs. highway), traffic, weather, driving habits, and fuel price fluctuations at the pump.
Maintain proper tire pressure, avoid aggressive acceleration and braking, reduce idling, remove excess weight, use cruise control on highways, and keep up with regular maintenance like oil changes and air filter replacements. Even small improvements can add up to significant savings over time.
Highway driving is generally more fuel-efficient because it involves fewer stops, starts, and speed changes. However, hybrid and electric vehicles often achieve better efficiency in city driving due to regenerative braking. The EPA provides separate city and highway MPG ratings for all vehicles sold in the US.