What Is a Good Readability Score? Grade Levels and Reading Ease Explained
A Flesch score of 60–70 is comfortable for most adults. A Flesch–Kincaid grade of 6–8 is the sweet spot for web writing. Here's how to interpret every common readability formula.
Run any piece of writing through a readability checker and you'll get back a number — maybe a 67.3, maybe a "grade level 9.4", maybe both. The numbers are precise. What they mean is a different question, and one that most readability tools answer badly.
This piece explains what each of the common readability formulas actually measures, what counts as a good score for what kind of writing, and the genuine limits of the metrics — because reading age estimates are useful, but they are not the same as actually being read.
The two flavours of readability score
Readability formulas come in two output styles:
Reading-ease scores produce a number on a 0–100 scale, where higher is easier. The Flesch Reading Ease formula is the most famous example. A score of 70 is described as "fairly easy to read"; a score of 20 is "very difficult".
Grade-level scores estimate the US school grade required to understand the text. A grade level of 8 means "an average eighth-grader (age 13–14) can read this". Flesch–Kincaid Grade Level, Gunning Fog, SMOG, and Coleman–Liau all output grade levels, with slightly different formulas.
The two flavours encode the same information. A 70 on Flesch Reading Ease corresponds roughly to a grade 7 reading level. They diverge at the extremes — reading-ease scores compress at the top, grade levels compress at the bottom — but for typical English prose they agree.
What "good" actually means
The headline rule is that there is no universally good score. There is only a score that matches your audience. With that established, here are the targets that show up across the plain-language literature:
| Audience | Flesch Reading Ease | Grade Level |
|---|---|---|
| Children (ages 8–10) | 90–100 | 4–5 |
| General public | 60–70 | 7–8 |
| Web content for adults | 60–80 | 6–8 |
| News journalism | 50–60 | 8–10 |
| Business writing | 50–60 | 10–12 |
| Government plain-language guidance | 60+ | 6–8 |
| Academic and professional | 30–50 | 13+ |
| Legal and technical | 0–30 | 14+ |
A few specific anchors that are widely quoted:
- The US Plain Writing Act of 2010 recommends government communications target a grade 6–8 reading level.
- The NHS plain English guidance in the UK targets a reading age of 9 (roughly grade 4–5).
- The Hemingway app flags any sentence at grade 10 or above as "hard to read".
- Reader's Digest is famously written to a grade 8 level; Time magazine to grade 9–10.
- Academic journal articles typically score grade 13–17 (US college level and above).
If you write for "general web audiences" without any narrower audience definition, grade 6–8 is the safest target. It's where Reader's Digest, the BBC, and most successful long-form blog content live.
The major formulas, briefly
There are dozens of readability formulas. Six show up everywhere; they're worth understanding because they sometimes disagree.
Flesch Reading Ease
Formula: 206.835 − 1.015 × (words/sentences) − 84.6 × (syllables/words)
Outputs a 0–100 score. Higher is easier. The two ingredients are average sentence length and average syllables per word — so the formula penalises long sentences and polysyllabic words equally.
A 60–70 score is considered "plain English", reachable by the average 13–15 year old.
Flesch–Kincaid Grade Level
Same inputs as Flesch Reading Ease, but rearranged to output a US grade level.
Formula: 0.39 × (words/sentences) + 11.8 × (syllables/words) − 15.59
It's the most cited grade-level formula and the one Microsoft Word reports by default. Slightly more pessimistic than Reading Ease at the high end.
Gunning Fog Index
Formula: 0.4 × (words/sentences + 100 × complex words/words)
Where "complex words" are those with three or more syllables (with some exclusions for common suffixes). Outputs a grade level. Fog tends to score higher than Flesch–Kincaid because it heavily weights syllable count.
The original purpose: Robert Gunning developed it in 1952 to measure the readability of business writing. He recommended a Fog Index of 12 or lower for general audiences.
Coleman–Liau Index
Formula: based on characters per word and sentences per 100 words, rather than syllables.
Coleman–Liau is the only common formula that doesn't count syllables. That makes it more reliable for languages or texts where syllable-counting is unreliable (e.g. heavy use of acronyms, proper nouns, or technical terminology). It's the formula the GPL3 software ships in many automated style tools.
SMOG Index
Formula: based on polysyllabic word counts across 30 sampled sentences.
SMOG was developed specifically for healthcare communications and is the formula most often cited in medical literacy research. It tends to score 2–3 grade levels higher than Flesch–Kincaid on the same text — partly by design, since SMOG estimates the grade level needed for complete comprehension, not just gist.
Dale–Chall Score
The odd one out: instead of counting syllables, Dale–Chall checks each word against a curated list of 3,000 words that "average fourth-graders know". Words outside the list are counted as "difficult".
This is the most labour-intensive formula but arguably the most realistic for everyday English. A specialist medical term might be only two syllables ("biopsy"), so syllable-counting formulas score it as easy — but Dale–Chall correctly recognises it as outside the common vocabulary.
A Dale–Chall raw score of 4.9 or below corresponds to "easily understood by an average 4th-grade student". Higher scores are mapped to grade ranges.
When formulas disagree
Run the same paragraph through six formulas and you'll often see two-grade-level spreads. The disagreements concentrate in three situations:
Short texts. All the formulas are statistical averages; they need a few hundred words of input to settle. A two-sentence draft can score wildly differently across formulas. The readability checker shows confidence indicators for short inputs.
Technical vocabulary in simple sentences. Syllable-based formulas (Flesch, SMOG) over-penalise short technical sentences ("Apply firmware update version 4.2.1.") because the proper nouns and numbers throw off syllable counts. Coleman–Liau and Dale–Chall handle this better.
Long sentences with simple words. "I went to the shop and I bought some bread and I came home and I made a sandwich and I sat down and I ate it." This is a long sentence of monosyllables. Sentence-length-weighted formulas (Flesch, Fog) flag it as hard; vocabulary-based formulas (Dale–Chall) flag it as easy. Both are right about different things.
The pragmatic answer is to read all the scores and look for consensus. If five out of six formulas put your text at grade 8, you're at grade 8. If the formulas disagree by three grades, look at what makes your text unusual — long sentences, technical terms, or proper nouns.
What readability scores don't measure
The numbers are a useful proxy. They are not the same as readable writing. Three things readability formulas miss completely:
Voice and rhythm. Hemingway scores well by every formula. So does Stephenie Meyer. They are not equally engaging. Formulas measure the floor of comprehensibility, not the ceiling of quality.
Logical structure. A grade-6 paragraph can be incomprehensible if the sentences are in the wrong order. Readability scores assume your argument is coherent; they don't check.
Reader motivation. A motivated reader will struggle through grade-16 prose. A bored reader will bounce off grade-6 prose. Audience interest beats audience reading ability nearly every time.
The most useful framing: readability scores tell you whether your prose is unnecessarily hard. They don't tell you whether it's good.
A workflow for using readability scores well
A defensible process for using these tools without becoming a slave to them:
- Write the draft without worrying about the score. Optimising on the way in creates flat, hedged prose. Get the ideas down.
- Run the draft through a checker. Don't focus on the headline number — read the which sentences are hard output. Long sentences are usually the biggest lever. The readability checker highlights difficult sentences inline.
- Rewrite the hard sentences. Usually means: split them into two. Sometimes means: replace one polysyllabic word with a shorter synonym. Almost never means: dumb down the content.
- Re-check. Your score should drop 1–2 grades for ten minutes of work. If it doesn't, the formula has caught something real and you may need to restructure rather than re-word.
- Read it aloud once. This catches what no formula catches — clunky rhythm, missing connective tissue, accidental repetition.
The honest summary
A "good" Flesch Reading Ease score is 60 or higher for general adult web readers, 70 or higher for plain-language guidance, 80+ for content aimed at less confident readers. A "good" grade level is 6–8 for the general public.
Anything in the academic or technical range (grade 13+) is fine if your readers are academics or technicians. The score isn't bad in itself — it's only bad if it doesn't match who is reading.
Run your writing through a checker. Don't chase a number. Use the which sentences are hard output to actually find the offenders. Then write the next paragraph.