LIX, called Lesbarhetsindeks in Norwegian, is the Scandinavian readability index used across Norwegian education to gauge how difficult a text is. Built originally for Swedish by C. H. Björnsson in the 1960s, it works for Norwegian Bokmål because it depends only on word length and sentence length, not on language-specific syllable rules. The same formula applies equally to Nynorsk.
The LIX formula
The index uses three counts: total words (W), total sentences (S), and the number of long words (L) — where a long word has more than six letters (seven or more characters).
LIX = (W / S) + (L × 100 / W)The first term is the average sentence length in words. The second is the percentage of long words. Adding them produces a single score that rises as sentences grow longer and as the vocabulary leans on longer words.
Interpreting your score
| LIX range | Difficulty | Typical Norwegian text |
|---|---|---|
| Below 25 | Very easy | Children’s books, early readers |
| 25 – 34 | Easy | Basic fiction, simple news, consumer instructions |
| 35 – 44 | Medium | Newspaper articles, general non-fiction |
| 45 – 54 | Difficult | Technical reports, academic textbooks |
| 55 and above | Very difficult | Laws, regulations, specialist scientific prose |
Norwegian school curricula use LIX to match texts to grade levels. For public-sector communication (Klarspråk guidance), the Norwegian government recommends targeting below 40 for citizen-facing documents.
Why Norwegian scores can run high
Norwegian Bokmål builds compound nouns as single written words: arbeidsmiljølov (Working Environment Act), personvernombud (data protection officer), gjennomsnittsinntekt (average income). Each is counted as one long word, directly inflating the long-word percentage. This is a genuine reflection of text density, not a flaw in the formula — dense compounds often do make Norwegian administrative prose harder to parse.
How to lower a LIX score
- Break long sentences first. Because average sentence length feeds directly into the formula as a simple addition, splitting one 25-word sentence into two 12-word sentences cuts several points immediately.
- Unpack compound nouns where it helps clarity. “Gjennomsnittlig inntekt” (average income) instead of “gjennomsnittsinntekt” replaces a long word with two shorter ones.
- Choose plain-word alternatives. “Bruk” instead of “benyttelse”, “vise” instead of “demonstrere” — shorter synonyms reduce the long-word share.
- Re-check after each edit. The LIX counter updates live, so you can see the effect of each revision immediately.
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