Fuel Economy Converter
Enter a value to instantly convert between fuel economy units.
Fuel economy conversions are essential for anyone comparing vehicles across countries — US and UK sources report fuel economy in miles per gallon (MPG), while most of the rest of the world uses liters per 100 kilometers (L/100km), and some countries use kilometers per liter (km/L). Unlike most conversions on this site, fuel economy conversions are not a simple multiplication: MPG measures distance per unit of fuel (higher is better), while L/100km measures fuel per unit of distance (lower is better) — converting between them requires an inverse (reciprocal) calculation.
1 MPG (US) = 235.2146 Liters per 100km
Key Formulas
MPG (US) → Liters per 100km
L/100km = mpg × 235.215Liters per 100km → MPG (US)
mpg = L/100km × 235.215Km per Liter → MPG (US)
mpg = km/L × 2.35215MPG (US) → Km per Liter
km/L = mpg × 0.425144Popular Conversions
All Fuel Economy Conversions
About Fuel Economy Conversions
History & Background
Miles per gallon became the standard fuel economy metric in the US and UK as cars became common in the early-to-mid 20th century, following naturally from each country's existing distance (miles) and volume (gallon) units. L/100km was adopted across most of Europe and many other countries as part of broader metrication, but importantly was defined as fuel-per-distance rather than distance-per-fuel — a deliberate choice that some argue better communicates fuel costs (a fixed distance, like a daily commute, has a fuel cost proportional to L/100km, whereas MPG requires more mental arithmetic to translate into cost). This different 'orientation' of the metric is the root reason the conversion isn't a simple multiplication.
How to Use This Converter
Enter a value in your starting unit and select your target unit for an instant conversion. Remember that because MPG and L/100km measure opposite things (distance-per-fuel vs. fuel-per-distance), a *higher* MPG corresponds to a *lower* L/100km — if your converted result seems to have the relationship backwards, double-check which unit you started from. Also note that 'MPG' can mean US or imperial gallons depending on the source; this converter uses US gallons by default.
Frequently Asked Questions
Why can't I just multiply to convert MPG to L/100km?
Because MPG measures distance per unit of fuel (higher = more efficient) while L/100km measures fuel per unit of distance (lower = more efficient) — these are reciprocal relationships, not directly proportional ones. The formula is L/100km = 235.215 / MPG (for US gallons), which means equal differences in MPG don't correspond to equal differences in L/100km — the relationship is non-linear. See our dedicated guide on MPG vs L/100km for a full explanation with worked examples.
What's the difference between US MPG and imperial (UK) MPG?
Both use 'miles' for distance, but the US gallon (3.785 L) and the imperial gallon (4.546 L) are different sizes — the imperial gallon is about 20% larger. As a result, the same car's fuel economy will show a higher number in imperial MPG than in US MPG, even though the actual fuel consumption is identical. Always check which gallon definition a figure uses before comparing across sources.
What is km/L and how does it relate to MPG and L/100km?
Km/L (kilometers per liter) is, like MPG, a distance-per-fuel metric (higher is better) — it's just MPG with metric units for both distance and volume. Converting km/L to L/100km is also a reciprocal calculation (L/100km = 100 / km/L), for the same reason as the MPG conversion: one measures distance-per-fuel and the other fuel-per-distance.
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