Frederick O'Loughlin

Dale–Chall Readability Scorer

Measuring the difficulty of a text using an algorithm

The Dale-Chall readability formula is intended to be a way of automatically checking the difficulty of a text. It calculates a score using:
- The number of 'difficult' words
- The total word count
- the number of sentences

Its a clever attempt to evaluate written word algorithmically, however it is much to rigid. the formula, while carefully balanced, focuses primarily on textual features. Yet 'difficulty' varies across subject, context and person - none of which are measured here. It also ignores other factors like flow and assumes correct spelling and grammar.

In other words. Written text is not a rigid item, so requires a more dynamic approach.

That being said its still can be fun to evaluate text this way and to try and break the formula. So I have made an online version available.

Let me give it a go