Fuel Economy Converter
Convert between US miles per gallon and litres per 100 kilometres, with the 235.215 constant and a worked example. Higher MPG means lower L/100 km.
Results
L/100km
- MPG (US)
- 30
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Educational estimates · not financial advice · free, no signup
Formula / how it works
L/100 km = 235.215 ÷ MPG (US). MPG (US) = 235.215 ÷ (L/100 km). The two scales are inverses, so a higher MPG corresponds to a lower L/100 km.
Read the guide: Unit Conversion Pitfalls: Metric, Imperial and Common Mistakes
Detailed guide
What it is, how to use it, how to read the numbers, common mistakes, a worked example, formulas, and FAQs.
What this calculator is
In the United States fuel economy is quoted as miles per gallon; most of the rest of the world uses litres per 100 kilometres. The scales run in opposite directions: a better car has a higher MPG but a lower L/100 km figure. This converter uses the constant 235.215, derived from the exact definitions of the mile and the US gallon. It handles US gallons only. A UK gallon is about 20% larger, so UK mpg figures are higher for the same car; use a converter that supports imperial gallons when you need them. It converts ratings, not real-world consumption, which depends on driving style, load and conditions.
When to use / who it helps
- You are reading a US spec and want a metric figure.
- You are comparing a car quoted in MPG with one quoted in L/100 km.
- You are estimating the fuel needed for a trip.
- You are travelling and renting a car.
- You are checking an economy figure in an article.
How to use
Steps
- Enter the value.
- Choose whether it is MPG (US) or L/100 km.
- Read the converted value.
- Do the reverse conversion as a check.
- Use the result with the trip distance to estimate fuel.
- Remember that US MPG and UK MPG differ.
How to interpret results
- Higher MPG is better; lower L/100 km is better.
- The relationship is a reciprocal, not a straight multiple.
- Small L/100 km changes at low consumption mean bigger MPG changes.
- Official ratings come from test cycles.
- Hybrid and electric vehicles use different measures.
Common mistakes & gotchas
- Treating the conversion as multiplicative rather than reciprocal.
- Using US MPG where UK MPG is intended.
- Assuming better MPG always means lower cost.
- Comparing ratings from different test standards.
- Rounding too early.
Worked example
Worked example — 30 MPG and 8 L/100 km
- 30 MPG: 235.215 ÷ 30 = 7.84 L/100 km.
- 8 L/100 km: 235.215 ÷ 8 = 29.4 MPG (US).
- A 500 km trip at 7.84 L/100 km uses 5 × 7.84 = 39.2 litres.
- For comparison, the same 30 MPG on the UK gallon scale is about 36 MPG.
Result: 30 MPG (US) equals 7.84 L/100 km.
To load the form's own demo values, tap Try example above the Calculate button.
How to calculate / formula
L/100 km = 235.215 ÷ MPG (US). MPG (US) = 235.215 ÷ (L/100 km). The two scales are inverses, so a higher MPG corresponds to a lower L/100 km.
Frequently asked questions
How do I convert MPG to L/100 km?
Divide 235.215 by the MPG figure.
Is higher MPG better?
Yes. For L/100 km, lower is better.
Why is 235.215 used?
It comes from 100 × 3.785411784 L per gallon ÷ 1.609344 km per mile.
What is the UK conversion?
Use 282.481 instead of 235.215 for imperial gallons.
Does this change with the vehicle's load?
The conversion does not, but real consumption does.
Why do I get a different MPG in real driving?
Speed, weather, traffic and driving style change fuel use.