Fuel Consumption Converter (L/100km, km/L, MPG)

Fuel consumption converter for L/100km, km/L, and MPG (US and Imperial)

Fuel economy is reported in different formats depending on the country, car manufacturer, or review site. In many places, fuel consumption is shown as L/100km (liters per 100 kilometers). In others, you will see km/L (kilometers per liter) or MPG (miles per gallon). The problem is that these units behave differently, and a number that looks “better” in one unit can look “worse” in another.

This calculator converts one fuel economy value into all common formats at once. The primary use is comparing two vehicles that were measured or advertised in different units. For example, you might have a spec sheet in L/100km but a forum post in MPG, or a local listing in km/L. Converting everything to one set of numbers lets you make a clean comparison without guessing.

How to use it is simple: enter the number you have, choose which unit it is, then press Convert. You will see L/100km, km/L, MPG (US), and MPG (Imperial). For interpretation, remember the direction: lower is better for L/100km, while higher is better for km/L and MPG. The results are purely unit conversions, so they do not change the underlying real-world consumption.

Assumptions and how to use this calculator

• This tool converts fuel economy units only. It does not estimate real-world consumption from driving style, traffic, tires, or terrain.
• MPG can mean US MPG or Imperial MPG. If your source is from the UK or uses “gallon” without clarification, choose Imperial to avoid a wrong conversion.
• L/100km is a “consumption per distance” unit, so lower values mean less fuel used for the same distance. km/L and MPG are “distance per fuel” units, so higher values mean more distance for the same fuel.
• If you enter a value that is extremely small or large, the math still works, but the number may not be realistic for a passenger vehicle. Treat extreme values as a signal to double-check your source.
• Rounding is shown to two decimals for readability. If you need more precision for engineering or research work, you should use the underlying formulas and more decimal places.

Common questions

Why do L/100km and MPG move in opposite directions?

They measure the same thing from different angles. L/100km is how much fuel you burn to go a fixed distance, so smaller is better. MPG is how far you go on a fixed amount of fuel, so larger is better. Converting between them involves a reciprocal relationship, which is why the direction flips.

What is the difference between MPG (US) and MPG (Imperial)?

The gallon size is different. An Imperial gallon is larger than a US gallon. That means the same vehicle will show a higher MPG number in Imperial MPG than in US MPG, even though it is not actually more efficient. This calculator outputs both so you can compare correctly.

My car shows km/L, but the spec sheet uses L/100km. Which should I trust?

Trust the measurement source, not the unit. Your car’s display is usually based on sensor estimates and can be biased by calibration and driving conditions. A spec sheet is often based on standardized test cycles that may not match your real driving. This tool only converts units so you can compare apples to apples within the same type of source.

Can I use this for diesel, petrol, or hybrid cars?

Yes, because it is just a unit conversion. Fuel type does not change the conversion math. What does change is real-world consumption, which depends on how and where you drive. For plug-in hybrids and EVs, the common unit may not be fuel-based at all, so this tool is not designed for those energy units.

How do I avoid mistakes when copying MPG from websites?

First, check whether the website is US- or UK-based and whether it uses US or Imperial gallons. Second, confirm whether the number is city, highway, combined, or a test-cycle figure. Then convert using the correct MPG type. If anything is unclear, use this tool to see both MPG outputs and keep your comparisons consistent.