Flesch Reading Ease

In plain English

One number, two ingredients: how many words you put in a sentence, and how many syllables you put in a word. Both go up, the score goes down.

Rough anchors: 90–100 is comfortable for a young child, 60–70 is plain English for a general audience, and anything under 30 is heavy going even for a specialist reader.

A worked example

The formula is 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words). Here it is on one sentence, counted by hand.

Sentence: "The committee reached a decision about the proposal."

words       = 8
sentences   = 1
syllables   = 3 + 1 + 1 + 3 + 2 + 3 = 13
            (com-mit-tee, the, a, de-ci-sion, a-bout, pro-po-sal)

206.835 − 1.015 × (8 ÷ 1) − 84.6 × (13 ÷ 8)
206.835 − 8.12 − 137.48
          = 61.2

61.2 lands in the plain-English band, which is about right for that sentence read aloud.

Notice how much weight the syllable term carries: 84.6 multiplied by a ratio near 1.6 removes 137 points, while the length term removes only 8. Polysyllables dominate this formula.

Rewrite it as "The committee decided on the proposal" and syllables per word drops to 1.5 while words per sentence drops to 6, lifting the score to about 74 — a real improvement, achieved by removing a buried verb rather than by shortening anything artificially.

Why it matters for AI detection

It is the score built into Microsoft Word and most writing tools, so it is the one people quote at each other without knowing what goes into it. Knowing the formula is two counts makes it much harder to over-read.

The syllable weighting is the practical takeaway. If you want the number to move honestly, replace long abstract nouns with verbs rather than hacking sentences in half.

It says nothing about whether text was written by a person or a machine, and no detector uses it. Any tool presenting a reading-ease score alongside an AI verdict is showing you two unrelated measurements side by side.

Commonly confused with

Flesch–Kincaid Grade Level

Same two ingredients, different arithmetic and an inverted scale. Reading Ease runs 0–100 with higher meaning easier; the Grade Level outputs a US school year, where higher means harder.

Readability

Readability is the general idea. Flesch Reading Ease is one specific formula for estimating it, and there are dozens of others that disagree with it.

Read next

• Readability checker
• Readability
• Nominalization