Numarly

Fuel Efficiency Converter (All-in-One)

Convert km/l, L/100km, mpg (US & UK) instantly

Converted Values

km/l: 20.00

L/km: 0.05

L/100km: 5.00

MPG (US): 47.04

MPG (UK): 56.50

Formula

Base unit: km/l

MPG (US) = km/l ÷ 0.425144

L/100km = 100 ÷ km/l

What is it?

This fuel efficiency converter converts between kilometers per liter (km/l), liters per 100 km, and miles per gallon (US & UK) simultaneously — useful for comparing car and bike fuel consumption.

Formula

  • 1 km/l = 2.35215 MPG (US)
  • 1 MPG (US) ≈ 0.425 km/l
  • L/100km = 100 ÷ km/l

Formula Explanation

km/l and MPG both measure distance per unit of fuel, so they scale directly by a fixed conversion factor. L/100km flips the relationship to measure fuel consumed per fixed distance instead, which is why it moves in the opposite direction — a lower L/100km means better efficiency, unlike km/l or MPG where higher is better.

Example Calculation

A car rated at 15 km/l converts to roughly 35.3 MPG (US), or about 6.67 L/100km.

How to Use

  1. Enter a fuel efficiency value.
  2. Select the unit.
  3. View the converted efficiency across all supported units instantly.

Benefits

  • Bridges metric (km/l, L/100km) and imperial (MPG) fuel economy standards.
  • Distinguishes US and UK gallons, which are different sizes.
  • Helps compare vehicle specs sourced from different countries.

Use Cases

  • Comparing a car's advertised fuel economy across regions.
  • Estimating fuel costs for a trip using a consistent unit.
  • Understanding manufacturer specs listed in an unfamiliar unit.

What Your Result Means

Each figure expresses the same fuel efficiency on a different scale. Remember that km/l and MPG increase with better efficiency, while L/100km decreases with better efficiency — they represent the relationship inversely.

Tips

  • Watch for whether a source uses US or UK gallons — they differ by about 20%.
  • Use L/100km when comparing fuel costs directly, since it scales with distance traveled.
  • Real-world fuel efficiency often differs from manufacturer specs due to driving conditions.

Common Mistakes

  • Mixing up US MPG and UK MPG, which represent different actual fuel economy for the same number.
  • Forgetting that L/100km is inverted — a smaller number means better efficiency, unlike the other units.
  • Comparing efficiency figures measured under different testing standards without noting the difference.

FAQs

Which is better, km/l or mpg?

Both measure the same thing — distance per unit of fuel — but km/l is commonly used in India and Europe, while mpg is standard in the US and UK.

Why is L/100km used?

L/100km shows fuel consumption rather than efficiency — a lower L/100km number means better fuel economy, which some people find more intuitive for comparing costs.

Is UK mpg different from US mpg?

Yes, the UK (imperial) gallon is larger than the US gallon, so the same fuel efficiency produces different mpg values between the two systems.

How much bigger is a UK gallon than a US gallon?

A UK (imperial) gallon is about 20% larger than a US gallon, which is why UK MPG figures are typically higher than US MPG for the same actual fuel efficiency.

Why does my actual fuel economy differ from the sticker rating?

Official ratings are measured under standardized test conditions; real-world factors like driving style, terrain, weather, and vehicle load can meaningfully change actual fuel economy.

What is a good L/100km value?

It depends on the vehicle type, but many modern passenger cars range from about 5-8 L/100km, with hybrids and small cars often below 5.

All conversions are based on standard unit definitions for US and UK measurements.

Last updated: July 25, 2026