Fuel Efficiency Converter
Enter a value in any field and all other units update instantly.
Trip Cost Calculator
Estimate your total fuel cost for a trip.
Fuel Needed
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Total Cost
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Cost per Mile/km
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Understanding Fuel Efficiency Units
Fuel efficiency measures how effectively a vehicle uses fuel, but different countries express it differently. The United States uses miles per gallon (MPG) with the US gallon of 3.785 liters, while the United Kingdom uses MPG with the larger Imperial gallon of 4.546 liters. This means the same car will have a higher UK MPG number than US MPG number, even though the actual fuel consumption is identical.
Most of continental Europe, Australia, and many other countries use liters per 100 kilometers (L/100km), which measures fuel consumption rather than efficiency. A lower L/100km number means better fuel economy. Japan and some other Asian countries use kilometers per liter (km/L). The key conversion relationships are: US MPG = 235.215 / L/100km, UK MPG = 282.481 / L/100km, and km/L = 100 / L/100km.
The trip cost calculator above helps you estimate how much fuel a journey will cost. Enter your trip distance, your vehicle's fuel efficiency in any unit system, and your local fuel price per gallon or per liter. The calculator converts everything internally and shows the total fuel needed, total cost, and cost per mile or kilometer, making it easy to budget for road trips or compare the running costs of different vehicles.
Frequently Asked Questions
What is the difference between US MPG and UK MPG?
US and UK MPG use different gallon sizes. A US gallon is 3.785 liters while a UK (Imperial) gallon is 4.546 liters. So a car getting 30 US MPG gets about 36 UK MPG. Always check which gallon is being referenced when comparing fuel economy figures.
How do I convert MPG to L/100km?
To convert US MPG to L/100km, divide 235.215 by the MPG value. For example, 30 US MPG equals 235.215 / 30 = 7.84 L/100km. For UK MPG to L/100km, divide 282.481 by the MPG value. The relationship is inverse: higher MPG means lower L/100km.
What is considered good fuel efficiency?
For conventional gasoline cars, 30+ US MPG (36+ UK MPG, under 7.8 L/100km) is considered good. Hybrid vehicles typically achieve 40-60 US MPG. Modern electric vehicles are rated differently using MPGe (miles per gallon equivalent).
Why do some countries use L/100km instead of MPG?
L/100km is used in most of Europe, Australia, and many other countries with the metric system. It measures fuel consumption directly, making it easier to calculate actual fuel costs for a trip. MPG measures efficiency inversely.