MPG to L/100 km Converter

How to use the fuel economy converter

What this calculator does

This calculator translates one fuel-economy or fuel-consumption value into four widely used units: Miles per US gallon, Miles per UK gallon, Liters per 100 kilometers, and Kilometers per liter. It is useful when comparing vehicle specifications from different countries, reading an imported vehicle listing, checking a dashboard display, or translating a road-test result. It performs unit conversion only; it does not predict your personal fuel bill, emissions, driving range, or real-world mileage. Those outcomes also depend on route, weather, speed, vehicle load, maintenance, and fuel price.

When to use it

Use the converter when a US vehicle listing gives mpg but a European comparison uses L/100 km; when a UK review reports imperial mpg; when a trip log records km/L; or when you want to check whether two apparently different ratings actually describe the same consumption. The US Environmental Protection Agency explains how official vehicle labels present fuel economy and related comparison information on its fuel economy label guide.

How to calculate

1. The calculator opens with a ready-to-use demonstration of 30 US mpg. All equivalent fields and the Excel workbook are already populated.
2. Replace any one field with your own positive decimal value. The field you edit becomes the source, and the other three update immediately.
3. Read the primary result and the four result cards. Remember that higher mpg or km/L means better efficiency, while lower L/100 km means better efficiency.
4. Review the conversion-detail table for a consistent four-decimal comparison.
5. Select Download Excel to save the current inputs and results as a validated .xlsx workbook. Reset clears all four fields and disables export until a complete valid value is entered again.

Input guide

Miles per US gallon is a required positive decimal when used as the source. It means miles traveled per US liquid gallon; 30 is a realistic example. A higher value lowers the equivalent L/100 km. Do not confuse the US gallon with the larger imperial gallon. Miles per UK gallon uses the imperial gallon; 36.03 UK mpg is equivalent to about 30 US mpg. Enter a positive decimal only. Liters per 100 kilometers is fuel consumed over 100 km; 7.84 is the startup example. Lower is more efficient. Do not interpret it like mpg, because its direction is reversed. Kilometers per liter is distance traveled per liter; 12.75 is the startup example. Higher is more efficient. Commas, scientific notation, zero, negative values, and mixed-unit text are rejected to avoid ambiguous parsing.

Output guide

Primary result repeats the active source unit so you can confirm which field drives the conversion. US fuel economy, UK fuel economy, and Metric fuel economy are distance-per-volume measures, so larger values indicate more travel from the same fuel volume. Fuel consumption is shown in L/100 km, so smaller values indicate less fuel used for the same distance. The two summary pills repeat the current US mpg and L/100 km values for quick scanning. Every output is an exact unit identity before display rounding, not a recommendation or forecast. The table's Efficiency direction column helps prevent the common mistake of treating L/100 km as though higher were better.

Worked example

At startup, the source value is 30 US mpg. Using exact distance and US-gallon definitions, kilometers per liter equals 30 × 1.609344 ÷ 3.785411784 = 12.7543 km/L. Liters per 100 kilometers equals 100 ÷ 12.7543 = 7.8405 L/100 km. Converting the same underlying distance and volume to an imperial gallon gives 36.0285 UK mpg. Those values match the first-open cards, table, and workbook. NIST recommends using exact conversion factors where available and rounding only after the calculation; its unit-conversion guidance explains that practice.