Flesch Reading Ease Score: Formula and How to Improve It

What is the Flesch Reading Ease score?

The Flesch Reading Ease and Flesch–Kincaid Grade Level are readability formulas designed to indicate how difficult a passage of written English is to understand. Rudolf Flesch created the Reading Ease test as a Plain English tool. Later, Flesch and the psychologist J. Peter Kincaid jointly developed the Grade Level test for the US Navy, in 1975.

Neither test reads for meaning. They look at the shape of the text, specifically its average sentence length and its average number of syllables per word, because longer sentences and longer words generally take more effort to read.

The Flesch Reading Ease formula

The formula is 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words). In plain terms, you start from a base number, subtract a penalty for each extra word in the average sentence, and subtract a larger penalty for each extra syllable in the average word.

Higher scores indicate easier text. The two inputs are easy to gather: count the words, the sentences, and the syllables in a sample, divide to get the averages, and plug them in.

How to read your score

Wikipedia reproduces the standard interpretation table, which links each score range to a school level. Remember that these are general bands for English text, not guarantees about any individual reader.

• 90 to 100: very easy to read, around 5th grade, easily understood by an average 11-year-old.
• 80 to 90: easy to read, around 6th grade, conversational English for consumers.
• 70 to 80: fairly easy to read, around 7th grade.
• 60 to 70: plain English, around 8th and 9th grade, easily understood by 13- to 15-year-old students.
• 50 to 60: fairly difficult to read, around 10th to 12th grade.
• 30 to 50: difficult to read, college level.
• 10 to 30: very difficult to read, best understood by college graduates.
• Below 10: extremely difficult to read, professional level.

Worked examples with real arithmetic

Suppose a passage averages 20 words per sentence and 1.5 syllables per word. The score is 206.835 − (1.015 × 20) − (84.6 × 1.5), which is 206.835 − 20.3 − 126.9, or about 59.6. That falls in the fairly difficult band.

Here are four illustrative passages. The averages are invented to show how the formula behaves, not measured from real text. The Grade Level column uses the Flesch–Kincaid formula described in the next section.

• 10 words per sentence and 1.2 syllables per word: Reading Ease about 95.2, Grade Level about 2.5.
• 12 words per sentence and 1.4 syllables per word: Reading Ease about 76.2, Grade Level about 5.6.
• 20 words per sentence and 1.5 syllables per word: Reading Ease about 59.6, Grade Level about 9.9.
• 25 words per sentence and 1.7 syllables per word: Reading Ease about 37.6, Grade Level about 14.2.

The Flesch–Kincaid Grade Level

The companion formula is 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59. It uses the same two inputs but expresses the result as a US school grade level instead of a 0 to 100 scale. A grade level of 9.9 means the passage is aimed at roughly a ninth or tenth grader.

Because both formulas use the same inputs, they move together: whatever makes the Reading Ease score rise also lowers the Grade Level. Pick whichever your team finds easier to explain.

What moves the score the most?

The formula shows exactly how much each habit is worth. Every word you remove from the average sentence adds about 1.015 points, so cutting the average from 20 words to 15 raises the score by roughly 5.1 points. Every 0.1 reduction in average syllables per word adds about 8.5 points.

Word length is a more powerful lever per unit, but it is harder to change, because you cannot make every word shorter without losing precision. Sentence length is the easier habit to control, and the one writers usually improve first.

How to improve your readability score

Digital.gov's plain language guidance emphasizes shorter words and short sections, and it says the present tense makes writing simpler, more direct, and more forceful. Its advice to write directly to the reader, saying You must do it rather than It must be done, also cuts words and removes passive phrasing.

Here is a before and after. The sentence We would like to take this opportunity to inform you that your application has been approved runs to 16 words. Your application has been approved says the same thing in 5.

• Aim for one idea per sentence, and split long sentences at conjunctions.
• Replace long or formal words with familiar ones, such as use instead of utilize.
• Prefer the present tense and active voice, and address the reader directly.
• Cut filler such as it should be noted that and in order to.
• Use short paragraphs, subheadings, and lists so readers can scan.
• Define jargon the first time you use it.
• Read the text aloud. Wherever you stumble or run out of breath, shorten.

Worked rewrite: one sentence, before and after

Here is a sentence from a typical official notice: In order to facilitate the efficient processing of your request, it is necessary that you submit all of the required documentation prior to the stated deadline. It has 26 words and several long, abstract ones, including facilitate, efficient, processing, and documentation.

A plain rewrite is Please send all required documents by the deadline. That is 8 words, with no formal vocabulary and a direct request.

The formula shows what the shorter sentence is worth. On the sentence-length term alone, going from 26 words to 8 is a drop of 18 words, and 18 × 1.015 is about 18.3 Reading Ease points. The shorter words add to the gain. Nothing was lost: the reader still learns what to send and by when, with less effort.

What score should you aim for?

There is no universal target. The right level depends on your readers and your subject. Writing for the general public usually benefits from the plain English band of 60 to 70, which Wikipedia's table describes as easily understood by 13- to 15-year-old students. Writing for specialists on a technical topic may naturally score lower, and that can be fine if your readers expect the terminology.

The mistake is chasing a number at the expense of accuracy. Do not strip out needed technical terms or oversimplify to hit a score. The aim is for your actual readers to understand you without extra effort.

Limits of readability scores

Wikipedia notes the main weakness. Readability formulas were developed for school books, and they show weaknesses compared with directly testing usability with typical readers. They neglect differences between readers and the effects of content, layout, and retrieval aids.

In practice that means a score cannot tell you whether information is accurate, well organized, or relevant. A string of very short, choppy sentences can score well and still read badly. Tools count syllables with rules of thumb, so the same text may score slightly differently in different programs, and numbers, names, and headings can distort the result. This guide makes no claim that a particular score changes search rankings. The benefit is for readers.

How to measure the score

You can calculate the score by hand for a sample, as in the worked example above, or use a tool that counts for you. Many writing tools and some word processors can report readability statistics. For consistency, measure the same sample size each time, such as a few hundred words, and compare scores between drafts rather than between different tools.

If your draft is unpublished or confidential, check it with software on your own computer or a tool that runs in your browser. Pasting private text into an unknown website sends it to someone else's server.