The New Dale-Chall formula was created to analyze readability for fourth-graders and above. But, where did it come from, and why should every writer be paying attention to it?

What is a New Dale-Chall readability score?

The New Dale-Chall readability score measures a text against a number of words considered familiar to fourth-graders. According to its scale, the more unfamiliar words used, the higher the reading level will be.

It is a similar system to Spache, which has a smaller list of familiar words and is more suitable for measuring texts for young children. Both of them calculate according to the same principle that word familiarity is an important aspect of readability.

Generally speaking, the lower the score,  the more readable the text for a fourth-grader. This differs from the Spache formula, which uses the same principle for children below fourth grade.

Where did the test come from?

The test was created by Edgar Dale and Jeanne Chall and was originally published in 1948. At the time, it sampled 763 words. This was updated in 1995 to expand the word list to over 3000 words. The formula was originally proposed in an article called ‘A Formula for Predicting Readability’ during a decade when many other formulas and their merits were being published.

The word list was revised as the New Dale-Chall formula and published because, as was pointed out in 1995, the original list only contained basic forms of verbs and nouns. The revisited version takes into account plurality and tense.

How does the test work?

As well as taking words and sentences into account as other readability formulas do, the words which fall outside of the word list (‘difficult’) words are compared to the number of familiar words in the text.

If the text has a number of difficult words (above 5% of the total words) the score is adjusted so that it is higher than the raw score.

In the pre-computer age, calculating Dale-Chall was fairly time-consuming. A sample of 100 words every ten pages of text was taken. This was then compared to the 3000-word New Dale-Chall list. Following this, the average sentence length had to be calculated as well as the percentage of unfamiliar words.

Thankfully, you can now use ReadablePro which analyzes the text as a whole. This saves you time and secures a more accurate score.

We keep it separate from our overall readability rating because of its specialist nature. For more generalized use, we recommend the widely recognized and validated Flesch-Kincaid score.

We combine Flesch-Kincaid with a bespoke combination of other accurate and respected algorithms to create a unique readability rating suited to a wide range of content.

If you are an elementary school educator or someone writing for a similarly accessible level (for example, short blogs, social media and emails) we recommend supplementing your overall analysis by keeping an eye on your New Dale-Chall score.

For your reference, here is the common words list used in the current version of the formula.

When is Dale-Chall most useful?

Making sure a text is suitable for fourth-graders is, as mentioned, important for teachers of this reading level.

However, New Dale-Chall has a surprisingly wide value for such a specialist calculation.

This is because readability is being increasingly recognized as essential to accessibility.

So much so that the UK Government recommends readable.io in their social media guidelines. Its guidelines state that content should be readable for a reading age of 9 years so that it can be easily comprehended.

This applies not only to children but also to people with additional learning needs.

As readability and accessibility go hand-in-hand, the fact that this minimum reading age of 9 years applies to fourth-grade students is important.

By using the New Dale-Chall readability framework, content writers can ensure their writing reaches a wide audience and is easily understood.

As Joseph Kimble has said about plain language:

“Plain language does not mean dumbing down. It means clear and effective communication.”

As a case study, we could all learn a lot from J.K. Rowling’s Harry Potter series. I put a PDF copy of The Sorcerer's Stone to the test to discover its New Dale-Chall readability score.

Overall, the book has a ReadablePro unique readability rating of ‘A’ (well done, Rowling.) I was also curious to know how suitable this is for fourth-graders to read and understand.

The Sorcerer's Stone’s New Dale-Chall score is 3.9. As this falls into the category of 4.9 or lower, the book can be easily understood by a fourth-grade student or lower, which means it’s very readable for elementary school students in general… a fact I can verify from my own experience!

ReadablePro’s ‘Quality’ tab also tells me that the overall tone and sentiment of the novel is conversational and positive, which contributes to the ease of reading.

A text is less easy to read when it is too formal, negative and dry. The Harry Potter series is so likable to all ages because it is so readable.

Harry Potter is also at a Flesch-Kincaid level of between 6 and 8. Content writers can learn so much from its approach because this is the same level as short blogs, social media and email.

Check out this handy blog post on how to use readability as a social media tool.

The great thing about the New Dale-Chall score is that it takes into account word familiarity. For general use, the Flesch-Kincaid Reading Age is the most popular and widely respected formula and combined with the other great formulas we use, it helps you fine-tune your writing for wide appeal.

The best way to use New Dale-Chall is for additional information on specific words in your text. This will enable you to identify comprehensive difficulty in a targeted way.

Maybe you’re doing this to aid your elementary teaching skill set. Maybe you’re using it to identify potential word swap-outs in your social media content. If this sounds like you, the New Dale-Chall formula is an invaluable tool to help you keep it readable.

Laura Kelly

Laura is an English MA graduate who loves language, unputdownable books, coffee and being a Customer Success Champion at Readable. Her hobbies include sightseeing, sketching, and film photography.