Flesch Reading Ease

The Flesch Reading Ease measures textual difficulty, which tells you how easy the text is to read.

Tools to calculate the Flesch Reading Ease include:

• Microsoft Word's grammar check
• Abiword (open source)
• KWord (open source)

How it works

The Flesch Reading Ease Scale measures readability as follows:

100: Very easy to read. Average sentence length is 12 words or fewer. No words of more than two syllables.

65: Plain English. Average sentence length is 15 to 20 words. Average word has two syllables.

30: Pretty difficult to read. Sentences will have mostly 25 words. Two syllables usually.

0: Extremely difficult to read. Average sentence length is 37 words. Average word has more than two syllables.

The higher the rating, the easier the text is to understand. By the very nature of technical subject matter, the Flesch score is usually relatively low for technical documentation. If you use the Flesch test regularly, you can soon get an idea of what a reasonable score is for the type of documentation you are working on. Aim to maximize the score. The approach to calculating the Flesch score is as follows:

1. Calculate the average sentence length, L.
2. Calculate the average number of syllables per word, N.
3. Calculate score (between 0-100%).

External link

• Rudolf Flesch, the developer of the test, provides some background information on how to write plain English.