Fuel Efficiency Converter

Convert between MPG (US/UK), L/100km, km/L, and more fuel efficiency units.

7.84047
L/100kmLitres per 100 km
12.7543
km/LKilometres per litre
30
MPG (US)Miles per gallon (US)
36.0286
MPG (UK)Miles per gallon (Imperial)
12.618
L/100miLitres per 100 miles
7.92518
mi/LMiles per litre
3.33332
gal/100miGallons (US) per 100 miles

Reference Vehicles

US gallon = 3.785 L · Imperial gallon = 4.546 L

How to Use

1

Select the fuel efficiency unit

Choose MPG (US), MPG (UK), L/100km, km/L, or miles/liter depending on your vehicle's documentation.

2

Enter the efficiency value

Type the fuel economy figure and all equivalent unit values appear instantly.

3

Compare vehicles

Convert multiple cars to the same unit to make fair international comparisons.

4

Calculate trip fuel costs

Combine converted efficiency with trip distance and fuel price per liter/gallon.

Understanding Fuel Efficiency

Fuel efficiency measures how far a vehicle travels on a specific amount of fuel. Different regions use different standards, which can cause confusion when comparing vehicle economy.

Fuel Efficiency Units

  • MPG (US): Miles per gallon (US). Higher is better
  • MPG (Imperial): Miles per gallon (UK). Higher is better
  • L/100km: Liters per 100 kilometers. Lower is better
  • km/L: Kilometers per liter. Higher is better
  • m/L: Miles per liter. Higher is better

MPG vs L/100km

MPG (miles per gallon) is used in the US and UK, where higher values mean better efficiency. L/100km is standard in Europe and most of the world, where lower values mean better efficiency. These inversely proportional scales can cause confusion when comparing vehicles across regions.

Key Conversion Facts

  • 1 US gallon = 3.785 liters
  • 1 Imperial gallon = 4.546 liters
  • To convert: US MPG × 0.425 = L/100km
  • To convert: L/100km ÷ 0.425 = US MPG

Frequently Asked Questions

Which is better: higher or lower fuel efficiency numbers?

It depends on the unit. Higher MPG is better (more miles per gallon). Lower L/100km is better (less fuel to travel 100 km). Always check the unit to understand what "better" means.

Why do US and UK use different gallons?

The US gallon (3.785 L) and imperial gallon (4.546 L) are different sizes due to historical reasons. This affects MPG calculations significantly.

How can I calculate my real fuel efficiency?

Fill your tank completely, record the odometer, drive normally, refill at the next tank purchase, and record the new odometer reading. Divide distance traveled by fuel purchased to get your actual efficiency.

What is typical fuel efficiency for cars?

Average modern cars get 25-35 MPG (US) or 8-11 L/100km. Hybrids can achieve 40-60+ MPG (US), while large trucks may only get 15-20 MPG (US).

Real-World Examples & Use Cases

Buying a Car from Another Country

International car listings and manufacturer specifications use different fuel economy units. A German car rated at 5.5 L/100km is equivalent to 42.8 MPG (US) or 51.4 MPG (UK). Without this conversion, comparing a European import against an American-market vehicle is nearly impossible. Buyers importing cars or reading international automotive reviews need accurate fuel economy conversion to make informed purchase decisions and estimate real-world fuel costs in their country.

Road Trip Fuel Cost Estimation

Planning a long road trip requires combining your vehicle's fuel efficiency with the trip distance and current fuel prices. A car getting 32 MPG (US) traveling 500 miles consumes approximately 15.6 gallons. At $3.50 per gallon, that is $54.60 in fuel. The same calculation in metric: 7.35 L/100km over 800 km consumes 58.8 liters. Converting between MPG and L/100km bridges this calculation for international travelers renting foreign vehicles or driving across unit-system borders.

Fleet & Commercial Vehicle Management

Logistics and transport companies managing international fleets need standardized fuel efficiency reporting. A truck fleet operating across the US (MPG) and Europe (L/100km) requires conversion to compare vehicle performance consistently. Fleet managers calculate total fuel budgets, identify underperforming vehicles, and benchmark against industry standards using a single metric. Converting all figures to L/100km or km/L allows consistent fleet-wide efficiency analysis regardless of where each vehicle was purchased.

EV vs ICE Range Comparison

Electric vehicles use energy efficiency units (miles per kWh or kWh/100km) that differ structurally from gasoline MPG. Understanding how an EV's 4 miles/kWh compares to a gasoline car's 35 MPG requires contextual energy cost conversion. While this converter handles traditional fuel units, understanding the conversion framework helps consumers see why direct MPGe (miles per gallon equivalent) figures are necessary — 33.7 kWh is defined as the energy equivalent of 1 US gallon of gasoline.

How It Works

Fuel efficiency units are NOT proportional — MPG and L/100km are inversely related: MPG (US) to L/100km: L/100km = 235.214 ÷ MPG (US) MPG (UK/Imperial) to L/100km: L/100km = 282.481 ÷ MPG (UK) Why is there a different constant? UK gallons are larger: - 1 US gallon = 3.78541 liters - 1 UK gallon = 4.54609 liters - 1 UK MPG = 1.20095 US MPG (20% better in US units) Key conversions: - 30 MPG (US) = 7.84 L/100km - 40 MPG (US) = 5.88 L/100km = 17.0 km/L - 5 L/100km = 47.04 MPG (US) = 56.49 MPG (UK) Inverse relationship: doubling MPG halves L/100km; improving from 10 to 20 L/100km saves the same fuel as improving from 5 to 6.67 L/100km at equal distances.

Frequently Asked Questions

Which is better — higher MPG or lower L/100km?▼
Both indicate better fuel efficiency. Higher MPG is better because a car traveling more miles per gallon uses less fuel. Lower L/100km is better because the car uses fewer liters to travel 100 kilometers. They are inversely proportional: a car with 40 MPG (US) uses 5.88 L/100km, while a car with 20 MPG uses 11.76 L/100km.
Why are US and UK MPG different?▼
The US and UK use different definitions of 'gallon.' The US gallon is 3.785 liters; the Imperial (UK) gallon is 4.546 liters. A car rated at 40 MPG (UK) only achieves approximately 33.3 MPG (US). When comparing cars from American and British sources, always specify which gallon is used.
What is good fuel efficiency for a car?▼
For a standard gasoline car, above 35 MPG (US) or below 6.7 L/100km is considered good. Hybrids typically achieve 45-60 MPG (US). For context: city driving uses more fuel than highway, and turbocharged smaller engines often beat larger naturally-aspirated engines in real-world efficiency.
How do I convert km/L to L/100km?▼
Divide 100 by the km/L value. L/100km = 100 ÷ km/L. Example: 12 km/L = 100 ÷ 12 = 8.33 L/100km. This unit is commonly used in Japan, parts of Asia, and some South American countries.
What is MPGe and how does it relate to L/100km?▼
MPGe (miles per gallon equivalent) rates electric vehicles against gasoline cars. The US EPA defines 33.7 kWh as equivalent to 1 gallon of gasoline in energy content. A car with 100 MPGe uses 33.7 kWh to travel 100 miles. This is separate from traditional L/100km conversion since electricity and liquid fuel are different energy forms.

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