LIX, or Læsbarhedsindeks in Danish, is the Scandinavian readability index created for Swedish and adopted across Danish and Norwegian education. It estimates how hard a text is from only word length and sentence length, which makes it reliable across languages without needing syllable rules.
How it works
LIX combines two measurements: the average sentence length and the percentage of long words. A long word has more than six letters. The score is:
LIX = (words / sentences) + (longWords × 100 / words)The first term is words divided by sentences. The second is the share of long words as a percentage. Summing them gives one index that grows as sentences lengthen and as the text uses more long words.
The LIX scale — what the numbers mean
| LIX range | Difficulty | Typical example |
|---|---|---|
| Under 25 | Very easy | Children’s early readers (letlæsning) |
| 25–34 | Easy | Fiction, simple news articles |
| 35–44 | Medium | General newspaper, non-technical blogs |
| 45–54 | Difficult | Academic introductions, specialist press |
| 55 and above | Very difficult | Legal text, ministerial circulars |
These bands are the conventional Danish interpretation. A government plain-language guide for public communications often targets a score under 40.
Why Danish scores higher than equivalent English text
Danish builds long compound nouns by joining words without spaces: trafikministeriet (the ministry of transport), arbejdsmarkedspolitik (labour market policy), skatteforvaltningen (the tax administration). Because LIX counts any word over six letters as “long,” these routine compounds push the long-word percentage up. English would typically split the same concept into two or three shorter words, yielding a lower LIX for the same semantic content. Comparing Danish LIX directly with English LIX benchmarks therefore tends to overstate difficulty.
How to lower a LIX score
- Split long sentences first. Average sentence length is usually the larger driver — breaking one 25-word sentence into two 12-word sentences can drop the score by several points.
- Unpack compound nouns. Replace one long compound with a short prepositional phrase: arbejdsmarkedspolitik → politik på arbejdsmarkedet reduces two long-word counts to one.
- Use active voice and verbs. Nominalisations (turning verbs into long nouns) are a hallmark of difficult administrative Danish; converting them back to verbs shortens words and loosens sentence structure simultaneously.
How LIX compares to other readability measures
LIX is dominant in Scandinavia but less known outside it. The main alternatives:
- Flesch-Kincaid (English-focused) uses syllable count, which varies by language and is harder to compute across non-English text. LIX’s long-word proxy is cruder but language-agnostic.
- SMOG and Coleman-Liau also depend on syllable or character counts tuned to English prose distributions.
Because LIX relies only on word count, sentence count, and a six-letter threshold, it is the most practical choice for cross-language readability comparison within the Scandinavian space. The same formula applied consistently to Danish, Swedish, and Norwegian texts produces comparable scores.
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