What this tool does
This tool converts fuel economy measurements between miles per gallon using the UK Imperial gallon and other common fuel efficiency units. The UK gallon (4.546 liters) is approximately 20% larger than the US gallon (3.785 liters), which means fuel economy figures differ significantly between the two systems. This converter handles the nonlinear relationship between consumption-based units like liters per 100 kilometers and distance-based units like miles per gallon, ensuring accurate results regardless of the direction of conversion. Users can convert between MPG (UK), MPG (US), kilometers per liter, liters per 100 km, and miles per liter with precision.
How it calculates
Conversions use the UK Imperial gallon (4.54609 liters) as the reference. For direct conversions: 1 MPG (UK) = 0.832674 MPG (US), 1 MPG (UK) = 0.354006 km/L, and 1 MPG (UK) = 0.219969 miles/L. The conversion to liters per 100 km is inversely proportional: L/100km = 282.481 / MPG (UK). The tool first converts any input to MPG (UK) as an intermediate base, then converts to the target unit. This two-step process ensures accuracy across all unit combinations.
Who should use this
- **UK and European drivers** comparing fuel economy ratings between vehicles sold in different markets - **Fleet managers** standardizing fuel consumption data across international operations - **Automotive journalists** converting manufacturer specifications for readers in different regions - **Travelers** understanding rental car fuel efficiency when driving abroad
Worked examples
Example 1: A UK car is rated at 45 MPG (UK). To find its US equivalent: 45 × 0.832674 = 37.47 MPG (US). Example 2: Converting 45 MPG (UK) to L/100km: 282.481 / 45 = 6.28 L/100km. Example 3: A European car rated at 5.5 L/100km converts to: 282.481 / 5.5 = 51.36 MPG (UK), or 51.36 × 0.832674 = 42.78 MPG (US).
Limitations
This tool assumes standard fuel measurement conventions and does not account for differences in testing methodology between regions (such as WLTP vs EPA test cycles). Actual fuel economy may vary based on driving conditions, vehicle load, and environmental factors. The conversions are mathematically exact but real-world fuel economy figures often differ from rated specifications.
FAQs
Q: Why are UK and US MPG values different? A: The UK uses the Imperial gallon (4.546 liters), while the US uses the smaller US gallon (3.785 liters). This means the same distance traveled on the same amount of fuel produces a higher MPG number in the UK system.
Q: Which measurement is more commonly used worldwide? A: Most countries outside the US and UK use liters per 100 kilometers (L/100km). This consumption-based metric is considered more intuitive because lower numbers indicate better efficiency.
Q: How do I compare cars rated in different systems? A: Enter the fuel economy value in its native unit using the "From" dropdown, select your preferred unit in the "To" dropdown, and the tool handles all conversions automatically.
Q: Is the conversion exact? A: The mathematical conversion is exact. However, official fuel economy ratings may differ between regions due to different testing protocols (WLTP in Europe vs EPA in the US).
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