LIX is the Scandinavian readability index, and it can be applied to Finnish because it relies only on word length and sentence length rather than syllables. The important caveat is that Finnish is agglutinative, so its words are unusually long and the index reads higher than for analytic languages like English.
How it works
LIX uses total words, total sentences, and the count of long words. A long word has more than six letters. The score is:
LIX = (words / sentences) + (longWords × 100 / words)The first term is the average sentence length in words. The second is the percentage of long words. In Finnish, case endings such as the inessive or elative, plus heavy noun compounding, push many ordinary words past seven letters, so the long-word percentage is structurally elevated.
LIX score bands (and the Finnish caveat)
The standard LIX scale was calibrated on Swedish and Danish texts, where ordinary writing sits in the 30–50 range. Finnish tends to run higher on the long-word component because of agglutination.
| LIX score | General label | Finnish context |
|---|---|---|
| below 25 | Very easy | Simple children’s texts; short words only |
| 25–34 | Easy | Simple Finnish prose, short sentences, basic vocabulary |
| 35–44 | Average | General news or fiction — a realistic target for Finnish |
| 45–54 | Difficult | Technical or formal Finnish; long compounds common |
| 55–64 | Very difficult | Administrative texts, contracts, specialist documents |
| 65 and above | Extremely difficult | Dense academic or legal Finnish |
A Finnish newspaper article scoring 45 should not be compared directly to an English article of the same score — the English piece is likely harder to read, while the Finnish score is inflated by grammar alone.
Why Finnish word length is structurally high
Finnish is an agglutinative language: meaning is built by attaching suffixes to a stem rather than using separate function words. The same concept that takes five words in English (in our houses as well) is expressed as a single word in Finnish (taloissammekin). This is not long-windedness — it is grammatical compression — but the LIX formula cannot distinguish a compound noun from a genuinely complex word.
Some examples of ordinary Finnish words that exceed the seven-letter threshold:
kirjastossa(in the library) — 11 lettersystävällinen(friendly) — 12 letterslukukelpoisuusindeksi(readability index itself) — 21 letters
How to improve a Finnish LIX score
Since LIX has two components, you have two levers:
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Shorten sentences. The average sentence length feeds directly into the formula. Breaking a 25-word sentence into two shorter ones is the single most effective action. Aim for around 15–18 words per sentence for average-difficulty Finnish.
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Prefer shorter vocabulary where grammar allows. You cannot always avoid long Finnish words — the grammar requires them — but technical jargon and academic compounds can often be replaced with simpler constructions. For instance, prefer
käyttö(use) overhyödyntämismahdollisuus(utilisation possibility). -
Avoid stacking multiple long compounds. A sentence heavy with multi-part compound nouns will push the long-word percentage very high. Break compounds into phrases or use a shorter synonym where one exists.
Compare your score against a target Finnish text of similar register rather than against English benchmarks. All counting and scoring runs locally in your browser — your text is never sent to a server.