Reading Level Analyzer

Five readability formulas disagree with each other on purpose. Flesch Reading Ease counts syllables per word, Gunning Fog counts words of 3 syllables or more, and Coleman-Liau ignores syllables entirely and counts letters. The Reading Level Analyzer runs all five over the same text so you can see where they converge, which is a far better signal than any single score.

The headline is Flesch Reading Ease, shown on a 0 to 100 gauge with a plain-English label and a target audience beneath it. Below that sit four counts and seven scores, including the averages the formulas are built from, so a bad number can be traced to whichever term produced it.

Three sample buttons load a simple passage, a news paragraph and an academic sentence, which span the range end to end. The whole analysis is arithmetic over the text in the box, with no upload.

Walkthrough: Three Samples, Three Verdicts

1. Press Simple. The gauge pegs at 100 and reads Very Easy, target audience 5th grade, on 20 words across 4 sentences with 0 complex words.
2. Press News, which is also what loads by default. Flesch drops to 31.7 and the label turns to Difficult, with a Flesch-Kincaid grade of 11.9 and a Gunning Fog of 17.8.
3. Press Academic. Flesch bottoms out at 0 while Flesch-Kincaid climbs to 30.3, which is the useful pairing: the ease score has nowhere left to go, and the grade score keeps counting.
4. Read the Complex Words card against the Gunning Fog row. The academic sample scores 13 complex words out of 19, and Fog is largely just that ratio.
5. Watch the SMOG row for the ⚠ needs 30+ sentences note. It appears on every one of the samples, because SMOG was calibrated on 30-sentence blocks and is guesswork below that.

The Five Formulas, Written Out

• Flesch Reading Ease is 206.835 minus 1.015 times words per sentence minus 84.6 times syllables per word, clamped into 0 to 100. The clamp is why the academic sample shows a flat 0.
• Flesch-Kincaid Grade is 0.39 times words per sentence plus 11.8 times syllables per word, minus 15.59. It uses the same two inputs as the ease score and converts them to a US school grade.
• Gunning Fog is 0.4 times the sum of words per sentence and the percentage of complex words. Complex here means 3 or more syllables, with no exemption for proper nouns or compounds.
• Coleman-Liau is 0.0588 times letters per 100 words, minus 0.296 times sentences per 100 words, minus 15.8. It never looks at syllables, which makes it the score to trust when the text is full of names.
• SMOG is 3 plus the square root of complex words scaled to a 30-sentence sample. Because it keys on complex words alone, it is the least sensitive of the five to sentence length.

Accuracy of the Syllable Heuristic

• Syllables are counted by rule, not by dictionary: drop a trailing e, then count runs of a e i o u y. Any word of 3 letters or fewer is assigned exactly 1.
• That rule undercounts adjacent vowels in separate syllables. area scores 2 where it should be 3, and idea the same.
• It overcounts silent vowels in the middle of a word, so business scores 3 rather than 2, which also promotes it into the complex-word tally and inflates Gunning Fog.
• Words with no true vowel scrape by on the y, so rhythm scores 1 rather than 2.
• Two of the five scores clamp at 0, and Flesch Reading Ease clamps at both ends, so a text can get harder without any of those three numbers moving. When a score sits exactly on 0 or 100, read the grade-level rows instead.