Coleman-Liau Index
The Coleman-Liau Index is a readability metric that indicates how difficult a text is to read based on the number of letters per word and words per sentence. Unlike most other indices, Coleman-Liau relies on characters instead of syllables per word because computer programs more readily and accurately count characters than syllables.
Values correspond to the number of years of education a reader requires to understand a text. For example, six corresponds to 11-12-year-old readers, while 12 corresponds to 17-18-year-olds. So, values should be interpreted as follows:
| Value | School level | Student age range | Notes |
|---|---|---|---|
| 0-1 | Pre-kindergarten - 1st grade | 3-7 | Basic level for those who just learn to read books. |
| 1-5 | 1st grade - 5th grade | 7-11 | Very easy to read. |
| 5-8 | 5th grade - 8th grade | 11-14 | A text is considered ideal for average readers. |
| 8-11 | 8th grade - 11th grade | 14-17 | Fairly difficult to read. |
| 11 and above | 11th grade - college | 17 and above | Too hard to read for the majority of readers. |
When dealing with technical documentation, the Coleman-Liau index returns lower values than other readability formulae.
Since it's based on the American Education system, school levels and age ranges may be inaccurate for non-English languages. However, it's still possible to compare the relative readability of two topics written in the same language.
| If a metric value is zero, make sure that the project language matches the content language and check the punctuation. |
Check out the other readeability metrics:
- Flesch-Kincaid Grade Level
- Flesch Reading Ease
- Gunning Fog Index
- Automated Readability Index
- Linsear Write
- SMOG Index
- FORCAST Grade
- New Dale-Chall Score
- Average Grade