What Is an MPG Calculator?
Miles per gallon (MPG) is the most common measure of a vehicle's fuel economy in the United States and United Kingdom. It tells you how many miles your car can travel on a single gallon of fuel. A higher MPG means a more efficient vehicle and lower fuel costs. This calculator divides the distance you drove by the fuel you used to give an exact figure.
How to Use It
Fill your tank completely and reset your trip odometer. Drive normally until the tank is low, then refill it completely again. The pump shows the gallons you just added — that's your fuel used. Read the miles from the trip odometer. Enter both numbers below and the calculator returns your real-world MPG along with the metric L/100 km equivalent.
The Formula
The calculation is simple division:
$$\text{MPG} = \dfrac{\text{Miles Driven}}{\text{Gallons Used}}$$For the metric conversion, the tool uses $$\text{L/100km} = \dfrac{235.215}{\text{MPG}}$$ where 235.215 is the standard conversion constant for US gallons.
Worked Example
Suppose you drove 300 miles and refilling your tank took 12 gallons. Your fuel economy is $$300 \div 12 = 25 \text{ MPG}$$ The metric equivalent is $$235.215 \div 25 \approx 9.41 \text{ L/100 km}$$
FAQ
Is this US or UK gallons? The MPG figure works for either, but the L/100 km conversion uses the US gallon (3.785 L). A UK gallon is larger (4.546 L).
Why is my real MPG lower than the sticker rating? City driving, cold weather, heavy loads, and aggressive acceleration all reduce efficiency compared to lab test conditions.
How can I improve my MPG? Keep tires properly inflated, remove excess weight, avoid hard braking, and maintain steady highway speeds.
