Lix (readability test)

LIX (abbreviation of Swedish läsbarhetsindex, "readibility index") is a readability measure indicating the difficulty of reading a text developed by Swedish scholar Carl-Hugo Björnsson. It is defined as a sum of two numbers: the average sentence length and the percentage of words of more than six letters.

$\text{LIX}=\text{average sentence length}+\text{percentage of words of more than six letters}$

Scores usually range from 20 ("very easy") to 60 ("very difficult").

The exact formula is:

$\text{LIX}=\frac{A}{B}+\frac{C\cdot 100}{A}$, where

$A$ is the number of words,

$B$ is the number of periods (defined by period, colon or capital first letter), and

$C$ is the number of long words (more than 6 letters).

Further reading

• Björnsson, C. H. (1968). Läsbarhet. Stockholm: Liber.
• Björnsson, C. H. (1971). Læsbarhed. København: Gad.

External links

• Detailed LIX calculator (in Swedish)