What is a gas mileage calculator?
A gas mileage calculator measures how efficiently your vehicle uses fuel. By comparing the distance you traveled with the amount of fuel you burned, it tells you your fuel economy. Two common ways to express this are miles per gallon (MPG), used in the United States, and liters per 100 kilometers (L/100km), used in most other countries. The tool works for cars, motorcycles, trucks, and any fuel-powered vehicle.
How to use it
Fill your tank completely and reset your trip odometer. Drive normally until you need to refuel, then fill up again. Enter the distance shown on the trip odometer and the amount of fuel it took to refill the tank. Choose your unit system and the calculator returns your MPG, L/100km, and distance traveled per unit of fuel.
The formula explained
Fuel economy is simply a ratio. To get MPG, divide the distance by the fuel used: \(\text{MPG} = \dfrac{\text{distance}}{\text{fuel}}\). To express consumption in metric terms, divide fuel by distance and scale to 100 km: \(\text{L/100km} = \dfrac{\text{fuel}}{\text{distance}} \times 100\). A higher MPG means better efficiency, while a lower L/100km means better efficiency.
$$\text{MPG} = \dfrac{\text{distance}}{\text{fuel used}} \qquad \text{L/100km} = \dfrac{\text{fuel used}}{\text{distance}} \times 100$$
Worked example
Suppose you drove 300 miles and used 12 gallons of gas. Your mileage is \(300 \div 12 = \) 25 MPG. If those same numbers were 300 km on 12 liters, your consumption would be \((12 \div 300) \times 100 = \) 4 L/100km, and your distance per liter would be 25 km/L.
$$300 \div 12 = 25 \text{ MPG} \qquad (12 \div 300) \times 100 = 4 \text{ L/100km}$$FAQ
Is higher MPG better? Yes — more miles per gallon means you use less fuel to travel the same distance.
How do I convert MPG to L/100km? They are inverse-style measures; this calculator shows both at once so you do not have to convert manually.
Why is my real-world mileage lower than the sticker? City driving, idling, heavy loads, and aggressive acceleration all reduce efficiency below the rated figure.
