Reading Level Checker

Every readability formula measures the same two things: how long the sentences are and how long the words are. Long sentences ask the reader to hold more in mind; long words tend to be less common. Neither says anything about whether the writing is clear, vivid or right for its subject, which is why a score is a prompt to look closer, not a verdict. The checker runs four published formulas, exactly as their authors wrote them:

Flesch also described what his Reading Ease scores mean in words, and the checker uses his labels: 90–100 very easy; 80–90 easy; 70–80 fairly easy; 60–70 standard; 50–60 fairly difficult; 30–50 difficult; below 30 very difficult. The three grade formulas give a US school grade, so 6 means a typical sixth grader (age 11 to 12) can read it. Because each formula leans on a different count, they rarely agree exactly; the checker shows their average as the headline grade.

Sources

1. Rudolf Flesch, “A new readability yardstick”, Journal of Applied Psychology 32(3), 221–233 (1948)
2. J. Peter Kincaid, Robert P. Fishburne Jr., Richard L. Rogers and Brad S. Chissom, “Derivation of New Readability Formulas (Automated Readability Index, Fog Count and Flesch Reading Ease Formula) for Navy Enlisted Personnel”, Research Branch Report 8-75, Naval Technical Training Command (1975)
3. Meri Coleman and T. L. Liau, “A computer readability formula designed for machine scoring”, Journal of Applied Psychology 60(2), 283–284 (1975)

The age-group fit under the scores is a rough guide we set from the school grades of each category’s readers, leaning toward the youngest, because a book has to work for the youngest child it is aimed at. A US grade is roughly a child’s age minus five or six.

• Picture book (read aloud) (ages 3–7): up to about grade 4. An adult reads it aloud, and children understand more by ear than they can read alone, so the text can sit above the listener’s own reading level. Rhythm and repetition matter more than the score.
• Early reader (ages 5–7): up to about grade 2. The child reads it alone, so short sentences and mostly one- and two-syllable words matter. Levelled series also control which words appear, which no formula checks.
• Chapter book (ages 6–9): up to about grade 4. Newly independent readers. Short chapters, plenty of dialogue and simple sentences, with the odd harder word explained by context.
• Middle grade (ages 8–12): up to about grade 6. Confident readers. Sentences can vary in length, but long, clause-heavy sentences slow younger readers in the range.
• Young adult (ages 12–18): up to about grade 9. Teen readers handle adult-level prose; most YA reads easily because it is voice- and dialogue-driven. The score cannot tell YA from adult fiction.
• Adult general readers (ages Adult): up to about grade 10. Plain-language guides commonly suggest aiming for around grade 8 when writing for the general public. Higher scores are normal in academic or technical writing, but they mean slower reading.

The formulas were not built for every kind of text, and some children’s books are exactly the kind they handle worst:

• Very short texts. Flesch worked with samples of about 100 words. A 300-word picture book has only a few dozen sentences, so one long sentence can swing the grade by a whole level.
• Verse and line-broken text. Rhyming picture books often have no full stops at the ends of lines. The formulas then see a few enormous sentences and report a grade far too high. Add punctuation where the sense ends before checking, or read the score loosely.
• Vocabulary. “Cat” and “cot” score the same, and so do “the” and “thy”. A text can score grade 1 and still use words a five-year-old has never heard. Levelled reader series use controlled word lists for this reason.

If you are unsure which category your book belongs in, the children’s book categories lesson explains each one, and the word count by genre table shows how long each usually runs.

When a score comes back higher than you want, the fix is almost never to swap in shorter words at random. Start with the longest-sentences list: it shows exactly where the formulas are being pushed up.

• Split sentences that do two jobs. A sentence that describes a room and then has a character act in it is usually two sentences. Splitting it lowers the grade and often makes the action land harder.
• Keep one long word where it earns its place. Children love a big word they can roll around (“enormous”, “catastrophe”). One per page is a treat; one per sentence is a wall.
• Prefer concrete words to abstract ones. “Frightened” and “scared” are a syllable apart, but “his hands shook” beats both, and the formulas reward it.
• Vary the rhythm. A run of five-word sentences is easy to read and tiring to hear. Aim for a low average with variety around it, not every sentence the same length.
• Read it aloud. If you stumble or run out of breath, a child will too. That test catches problems no formula can.

Going the other way matters too. A middle grade or YA draft that scores grade 3 throughout may feel flat to older readers; a few longer sentences in moments of reflection can give the prose room to breathe.

A sentence ends at a full stop, question mark or exclamation mark followed by a new sentence, or at a blank line. Titles and abbreviations such as “Mr.”, “Dr.”, “e.g.” and “U.S.”, initials such as “J. K.”, and decimals such as “3.5” do not end a sentence, and a dialogue tag stays with its line, so “Help!” she cried counts as one sentence. Curly quotes, dashes and ellipses are handled the same as their plain forms.

Syllables are counted by rules rather than a dictionary: vowel groups, corrected for silent endings (“make”, “jumped”), for vowel pairs that split (“li-on”, “ra-di-o”) and for a list of common exceptions. It gets everyday words right, but some names, loanwords and words with regional pronunciations (“chocolate”, “every”) will be off by one. Averaged over a few hundred words, that moves a grade by a tenth or two. Long words in the stats are words of three or more syllables.

Writing for children? The children’s story generator drafts a short story for an age group you choose, and the AI children’s book maker turns an idea into a finished, illustrated picture book with narration. Paste its pages back here to check the level.