Fuel Economy Unit Converter

Categories: Tools & Calculator

Convert fuel economy and consumption values across different units: US MPG, UK Imperial MPG, Liters per 100 Kilometers (L/100km), and Kilometers per Liter (km/L).

Fuel Economy Unit Converter

Please enter a valid positive numerical value.

Converted Fuel Economy Ratings

US Miles Per Gallon (US MPG): 0.00 MPG
UK Imperial Miles Per Gallon (UK MPG): 0.00 MPG
Liters Per 100 Kilometers (L/100km): 0.00 L/100km
Kilometers Per Liter (km/L): 0.00 km/L

The Conversion Equations

Fuel economy metrics are generally categorized into two methodologies: Economy (distance traveled per volume of fuel) and Consumption (volume of fuel burned over a set distance). Converting between them requires distinct scaling factors:

1. Converting Between US MPG and UK Imperial MPG

Because the United Kingdom uses a larger gallon measurement than the United States, UK MPG values are mathematically higher than US MPG values for the same vehicle efficiency:

UK MPG = US MPG × 1.20095US MPG = UK MPG ÷ 1.20095

2. Converting US MPG to Liters Per 100 km (L/100km)

To convert from an imperial distance-per-fuel metric to a metric fuel-per-distance metric, utilize the standard scaling constant 235.215:

L/100km = 235.215 ÷ US MPGUS MPG = 235.215 ÷ L/100km

3. Converting km/L to US MPG

Both parameters measure distance traveled over a unit of volume. To scale between kilometers per liter and miles per US gallon:

US MPG = km/L × 2.35215km/L = US MPG ÷ 2.35215

4. Converting L/100km to km/L

Both are metric, but one measures consumption while the other measures economy. Convert by dividing 100 by the value:

km/L = 100 ÷ L/100kmL/100km = 100 ÷ km/L

Fuel Economy Quick Reference Conversion Table

The table below provides exact conversions between the four major global fuel economy units, mapped to common automotive milestones.

US MPGUK MPG (Imperial)Metric L/100kmMetric km/L
10.0 MPG12.01 MPG23.52 L/100km4.25 km/L
15.0 MPG18.01 MPG15.68 L/100km6.38 km/L
20.0 MPG24.02 MPG11.76 L/100km8.50 km/L
25.0 MPG30.02 MPG9.41 L/100km10.63 km/L
30.0 MPG36.03 MPG7.84 L/100km12.75 km/L
35.0 MPG42.03 MPG6.72 L/100km14.88 km/L
40.0 MPG48.04 MPG5.88 L/100km17.01 km/L
50.0 MPG60.05 MPG4.70 L/100km21.26 km/L

Contextual Information & Regional Differences

The US vs. UK Gallon Difference

A common point of confusion when comparing vehicle specifications is the difference in MPG ratings between the US and UK markets. This occurs because the standard units of volume differ [5]:

  • US Liquid Gallon: Equals 3.785 liters.
  • UK Imperial Gallon: Equals 4.546 liters (roughly 20% larger than the US gallon).

Because the UK gallon holds more fuel, a car driving in the UK will travel farther on "one gallon" of fuel than the exact same car driving in the US, making the UK MPG rating appear higher despite identical engine efficiency.

Economy vs. Consumption

Understanding whether a unit measures economy or consumption helps interpret vehicle efficiency trends:

  • Economy (MPG, km/L): Measures distance over fuel. Higher numbers mean better efficiency. It is intuitive for calculating range (how far can I go on a tank?), but it does not scale linearly with fuel costs, sometimes distorting consumer understanding of efficiency improvements.
  • Consumption (L/100km): Measures fuel over distance. Lower numbers mean better efficiency. This is the standard throughout Europe, Canada, and Australia. It scales linearly with fuel costs, making it simple to calculate exactly how much money a change in vehicle consumption will save over a long-term driving distance.

Automotive Calculator List

Engine & Horsepower Calculators

Fuel & Fuel Economy Calculators

Unit Conversion Calculators

Vehicle Loan Calculators

Wheels & Tires Calculators