Dale–Chall readability calculator

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Words per sentence: JavaScript must be enabled
Percentage of difficult words: JavaScript must be enabled
Dale–Chall readability score: JavaScript must be enabled
Difficult words:
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The Dale–Chall readability formula is useful for getting a quick measure of Readability.


The adjusted score roughly means:

The grades refer to American students, where 4th grade is a 9-year-old.

The main use I’ve found for the tool is highlighting words that aren’t common, prompting me to think about whether they’re needed.

I aim for my writing to have a score below 8. This isn’t easy, and in some cases isn’t worth it.

You might think that number is too low. Surely my target audience is at least high-school graduates?

Firstly, it’s only a target, and I often miss it without stressing about it.

Secondly, everything I write starts with plenty of words that can be cut or changed with no cost to clarity. Those can go right away. Why wouldn’t I make my writing more readable, if it comes at no cost? (Other than the time I spend editing, of course.)

Most importantly, readability isn’t just a binary Yes/No “Can the reader read this?” A 12th grade student will find it easier to read something with a score of 7 than a score of 8, even if they are capable of reading both. The less effort my reader spends reading, the more effort they can spend thinking about what the writing says.


The formula was first published in 1948, long before computers. Doing the calculation by hand takes a while, so testers would only test short samples of the text instead of doing the whole thing, and even then it was tedious. But it did have the upside that the human could handle weird input. Computers are not so good at that.

This calculator uses these rules to clean up the input:

In Using a Computer to Calculate the Dale-Chall Formula, it says:

In addition, 5) names of persons and places are considered familiar even though they do not appear on the list; 6) names of organizations, laws, documents, titles of books or movies, when used several times in a sample of 100 words, are counted only twice.

For computers, this is not easy. This calculator doesn’t attempt to decide if a word is a proper noun, and it definitely doesn’t try to decide what type of proper noun it is.