Fuel Consumption Conversion Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/10/2026
To convert a consumption to MPG, divide 235.21 by the value in L/100km for a US gallon, or 282.48 for an imperial gallon (UK). A consumption of 6 L/100km therefore equals about 39.2 MPG (US) or 47.1 MPG (UK).
Explanation
Liters per 100 km (L/100km) and miles per gallon (MPG) measure the same thing — a vehicle's fuel efficiency — but in inverse ways: the lower the L/100km consumption, the better the efficiency, while the higher the MPG, the better the efficiency. That is why the relationship between the two is not linear but inversely proportional. **Important point of vigilance**: there are two different definitions of the gallon, which gives two distinct MPG results for the same consumption. The US gallon (3.785411784 liters) is used in the United States and Canada; the imperial gallon (UK gallon, 4.54609 liters, about 20% larger) is used in the United Kingdom and other Commonwealth countries. A vehicle showing "40 MPG" in the United States and another showing "40 MPG" in the United Kingdom therefore do not have the same real consumption: the British figure corresponds to a consumption about 20% lower, at equal displayed MPG — a frequent confusion when comparing consumption figures found in sources from different countries.
Example: converting 6 L/100km
Inputs
Consumption: 6 L/100km.
Calculation
MPG (US) = 235.214583 ÷ 6 ≈ 39.20. MPG (UK) = 282.480936 ÷ 6 ≈ 47.08.
Result
This consumption equals about 39.2 MPG (US) or 47.1 MPG (UK).
Frequently asked questions
Why is the British MPG higher than the American MPG for the same real consumption?
Because the imperial gallon (used in the UK) contains about 20% more liters than the US gallon. For the same distance traveled on the same amount of fuel, the number of "imperial gallons" consumed is therefore smaller than the number of "US gallons", which mechanically gives a higher British MPG, while the real consumption in L/100km is identical.
Where do the constants 235.21 and 282.48 come from?
They derive from three unit conversions that are exact by definition: 1 mile = 1.609344 km, 1 US gallon = 3.785411784 L, 1 imperial gallon = 4.54609 L. Combining these three values (100 km converted to miles, multiplied by the number of liters in a gallon) gives these two constants used in the formula directly.
Does this conversion account for the type of fuel (gasoline, diesel)?
No, this conversion is purely an equivalence of volume and distance units, independent of the fuel used. It reflects no difference in energy content per liter between gasoline and diesel — it faithfully converts any consumption expressed in L/100km, whatever the fuel.