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

Fuel consumption converter for km/L, L/100km, and MPG

This fuel consumption calculator converts common fuel economy units so you can compare like for like. Different countries and car dashboards report fuel use in different formats. Many drivers see km/L in parts of Africa and Asia, L/100km in much of Europe and Australia, and MPG in the United States and the United Kingdom. If you are researching a car online, comparing your own logbook against manufacturer claims, or checking whether a road trip estimate looks realistic, the first problem is usually the unit mismatch. This converter fixes that.

Use it by selecting the unit you already have, typing your value, and pressing Convert. The calculator will return all equivalent units at the same time: km/L, L/100km, and both MPG versions. That last part matters because “MPG” is ambiguous. US MPG uses a US gallon, while UK MPG uses an Imperial gallon. The numbers are not directly comparable unless you specify which gallon was used. This tool shows both outputs so you can match what you are reading.

The outputs tell you the same story in different ways. km/L and MPG are “more is better” units: higher means you travel further for each liter or gallon. L/100km is the opposite: lower means you burn fewer liters to travel 100 km. If you are used to one system, converting can reduce confusion. For example, a value that looks small in km/L may still be a good result once you see the equivalent L/100km, and vice versa. Converting also helps when people share fuel economy in forums, reviews, or when you import a vehicle and want to validate expected running costs.

Assumptions and how to use this calculator

• All conversions are mathematical unit conversions only. They do not adjust for driving style, terrain, weather, or vehicle load.
• If you enter MPG, choose whether your input is US MPG or UK MPG so the conversion uses the correct gallon definition.
• Values must be greater than 0. Fuel economy cannot be zero or negative.
• L/100km is calculated from km/L using the standard relationship: L/100km = 100 ÷ (km/L).
• Displayed results are rounded to two decimals for readability.

Common questions

What is the difference between US MPG and UK MPG?

They use different gallon sizes. A UK (Imperial) gallon is larger than a US gallon, so the same real-world fuel use produces a higher number in UK MPG than US MPG. If you compare MPG figures without knowing which one is used, you can draw the wrong conclusion about efficiency.

Why does L/100km work the opposite way to km/L?

Because it measures consumption instead of distance-per-fuel. L/100km answers: “How many liters do I burn to travel 100 km?” Lower is better because you are consuming less fuel to cover the same distance. km/L answers: “How far can I go on one liter?” Higher is better because you travel further per unit of fuel.

Which unit should I use for tracking my own fuel economy?

Use the unit that matches your dashboard and fuel receipts so you make fewer mistakes. If your odometer is in kilometers and you buy fuel in liters, km/L and L/100km are both natural fits. Many drivers prefer L/100km because it maps more directly to cost per distance, but km/L can feel more intuitive for quick comparisons. The key is to stick to one unit for your personal tracking and convert when comparing with external sources.

Are manufacturer fuel economy claims directly comparable to my real driving results?

Often not. Manufacturer figures are usually measured under controlled test cycles, which can differ significantly from real conditions. Your results can vary based on speed, traffic, air conditioning use, tire pressure, altitude, payload, and maintenance. The unit conversion is still valid, but the real-world number may differ from the published one.

How do I convert quickly without doing math?

Use this calculator. The biggest manual pitfall is mixing up US MPG vs UK MPG or inverting the relationship between km/L and L/100km. This tool handles those details and outputs all units together so you can sanity-check the results.