Authoritative definitions of the International System of Units and SI prefixes.
Dedicated unit pair
Miles per US gallon to Miles per imperial gallon
Convert mpg (US) to mpg (imp) instantly, then review the formula, assumptions, and rounding guidance.
Fuel consumption & efficiencyInstant result
Decimals
Formula Convert mpg (US) to litres per 100 kilometres, then convert to mpg (imp). 1 mpg (US) = 1.2009 mpg (imp)
Common examples
One value, several units
Litres per 100 kilometres235.2146 L/100 km
Miles per imperial gallon1.2009 mpg (imp)
Kilometres per litre0.4251 km/L
Conversion table
| mpg (US) | mpg (imp) |
|---|---|
| 1 mpg (US) | 1.2009 mpg (imp) |
| 2 mpg (US) | 2.4019 mpg (imp) |
| 5 mpg (US) | 6.0047 mpg (imp) |
| 10 mpg (US) | 12.0095 mpg (imp) |
| 25 mpg (US) | 30.0237 mpg (imp) |
| 50 mpg (US) | 60.0475 mpg (imp) |
| 100 mpg (US) | 120.095 mpg (imp) |
Conversion chart
1 mpg (US)1.2009 mpg (imp)
5 mpg (US)6.0047 mpg (imp)
10 mpg (US)12.0095 mpg (imp)
25 mpg (US)30.0237 mpg (imp)
50 mpg (US)60.0475 mpg (imp)
Worked example
8 L/100 km is approximately 29.4 US mpg.
Unit definition
Miles per US gallon (mpg (US)) This unit is defined through the displayed non-linear relationship to litres per 100 kilometres.
Unit history
Miles per US gallon is represented here using its modern SI definition or an internationally accepted relationship to an SI base unit.
Step by step
1. Parse the value, including fractions.
2. Convert mpg (US) to litres per 100 kilometres.
3. Convert the base value to mpg (imp) and apply your display precision.
Important
Fuel economy and fuel consumption are reciprocal measures; zero is not a valid input.
Understand the result before using it
Miles per US gallon to Miles per imperial gallon converts a value measured in Miles per US gallon (mpg (US)) into the equivalent value in Miles per imperial gallon (mpg (imp)). The numerical value changes because the size and definition of the selected unit changes; the underlying quantity does not.
Calculated result
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.
Formula, assumptions, and example
Formula
Convert mpg (US) to litres per 100 kilometres, then convert the base value to mpg (imp).
Assumptions
- Miles per US gallon and Miles per imperial gallon represent the same fuel consumption & efficiency quantity.
- The input is expressed in mpg (US); the output is expressed in mpg (imp).
- Fuel economy and fuel consumption are reciprocal measures; zero is not a valid input.
Worked example
1 mpg (US) = 1.2009499258 mpg (imp). For another value, apply the same relationship and round only to the precision your source measurement supports.
When to use it
Good uses
- Read a mpg (US) measurement in a document that expects mpg (imp).
- Compare a miles per us gallon value with a value reported in miles per imperial gallon.
- Check the mpg (US)-to-mpg (imp) arithmetic before copying the result into another calculation.
Limitations
Common mistakes to avoid
- Fuel consumption and fuel economy are reciprocal; zero and negative values are not physically valid inputs.
- Round the output to a precision justified by the original measurement.
- Verify safety-critical, regulated, laboratory, and contractual conversions against the controlling standard.
Sources and further reading
These references explain the underlying standards or provide authoritative context. Your own contract, institution, clinician, product documentation, local code, or governing standard may be the controlling source.
Guidance on unit names, symbols, conversions, and numerical presentation.
Questions about this calculation
How do I convert Miles per US gallon to Miles per imperial gallon?
Convert mpg (US) to litres per 100 kilometres, then convert the base value to mpg (imp). Using the displayed relationship, 1 mpg (US) equals 1.2009499258 mpg (imp).
How many Miles per imperial gallon are in one Miles per US gallon?
One Miles per US gallon is 1.2009499258 Miles per imperial gallon. The displayed digits may be rounded.
Can I reverse the mpg (US) to mpg (imp) conversion?
Yes. Swap the source and target units in the converter. The reverse relationship converts mpg (imp) back to mpg (US).
Is the Miles per US gallon to Miles per imperial gallon result exact?
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.