Rate Index (RIX) readability formula

The Rate Index (RIX) readability formula is useful because it can be used on documents of any Western European language. This test calculates an index score of a text sample based on sentence count and number of long words (i.e., words containing seven or more characters).

The RIX Formula

RIX = LW/S

Where:

RIX RIX index score

LW Number of long words (7+ characters)

S Number of sentences

RIX Index Table

7.2 and above	College
6.2 and above	12
5.3 and above	11
4.5 and above	10
3.7 and above	9
3.0 and above	8
2.4 and above	7
1.8 and above	6
1.3 and above	5
.8 and above	4
.5 and above	3
.2 and above	2
Below .2	1

Citations

Anderson, Jonathan (1981). 'Analysing the Readability of English and Non-English Texts in the Classroom with Lix'.

Anderson, Jonathan (1983). 'Lix and Rix: Variations of a Little-Known Readability Index', Journal of Reading, 26, 6, 490-496