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Fuel Efficiency guide

The Fuel Efficiency Converter translates fuel economy ratings between miles per gallon (US and UK), liters per 100 kilometers, and kilometers per liter.

Worked examples

Convert US MPG to L/100km

  1. Enter 30.
  2. Choose US MPG (mpg) as the From unit.
  3. Choose L/100km as the To unit.
Result: 30 US MPG = 7.8405 L/100km

To convert MPG to L/100km, divide 235.215 by the MPG. 235.215 / 30 = 7.8405.

Convert L/100km to UK MPG

  1. Enter 5.
  2. Choose L/100km as the From unit.
  3. Choose UK MPG (mpg) as the To unit.
Result: 5 L/100km = 56.4963 UK MPG

5 L/100km is excellent fuel economy. 282.481 / 5 = 56.4963 UK MPG.

Compare US and UK MPG

  1. Enter 50.
  2. Choose UK MPG as the From unit.
  3. Choose US MPG as the To unit.
Result: 50 UK MPG = 41.6331 US MPG

A UK gallon is larger, so the same car will always have a higher UK MPG rating than its US MPG rating.

Tips

  • •Higher MPG is better. Lower L/100km is better.
  • •L/100km is an inverse measurement, meaning it has a reciprocal relationship with MPG.
  • •To get a quick mental estimate, divide 235 by the US MPG to get the approximate L/100km.

Frequently asked questions

What is MPG?
Miles per gallon. It measures how far a car can travel on one gallon of fuel.
What is L/100km?
Liters per 100 kilometers. It measures how much fuel is consumed to travel 100 kilometers.
Why is L/100km inverted compared to MPG?
MPG measures distance per unit of fuel. L/100km measures fuel per unit of distance. They are reciprocal metrics.
What is the difference between US and UK MPG?
A US gallon is 3.785 liters, while a UK gallon is 4.546 liters. Therefore, a car will get a higher MPG number in the UK.
How do I convert MPG to L/100km manually?
Divide 235.215 by the US MPG (or 282.481 by the UK MPG).
What is a good MPG?
For gas cars, anything above 30 US MPG is considered good. Hybrids often get 50+ US MPG.
What is km/L?
Kilometers per liter. It is a metric unit of distance per fuel, often used in Asia and South America.
Why do electric cars not use MPG?
They use MPGe (Miles Per Gallon equivalent), which compares the energy in one gallon of gas to the equivalent energy in electricity.
How does speed affect fuel efficiency?
Fuel efficiency usually peaks around 50-60 mph (80-100 km/h) and decreases at higher speeds due to aerodynamic drag.
Can I convert from L/100km to km/L?
Yes. 100 divided by the L/100km value gives the km/L value.
Is the calculator accurate for all vehicles?
It converts the units perfectly, but real-world vehicle efficiency depends on driving habits, terrain, and weather.
What is a high L/100km number?
Anything over 12 L/100km is considered heavy fuel consumption (e.g., large trucks or older sports cars).
How many liters are in a US gallon?
Exactly 3.785411784 liters.
How many liters are in a UK gallon?
Exactly 4.54609 liters.
How do I calculate fuel cost per mile?
Divide the price of gas per gallon by your car’s MPG rating.
What is the best unit for comparing cars globally?
L/100km is generally preferred for scientific comparison, but MPG is more common in the US.
Why does the US use MPG?
It is a historical standard. Most of the rest of the world uses the metric system (L/100km).
Are the results rounded?
Yes, to 4 decimal places.
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