How hard is a text to read? Flesch’s formula weighs two things: how LONG the sentences are, and how many SYLLABLES the words carry. Short sentences of short words score high (easy); long sentences of polysyllables score low (a scientific paper). Slide from a children’s line to dense academic prose and watch the gauge drop.
Flesch Reading Ease = 206.835 − 1.015·(words/sentence) − 84.6·(syllables/word). Higher is easier: 90–100 is 5th-grade plain English, 60–70 standard, 30 and below is college/academic, and it can go negative for very dense text. It captures only two surface signals — sentence length and word length — yet tracks perceived difficulty well. A fail-loud self-check throws unless a short-word, short-sentence text scores higher than a long-word, long-sentence one. ◆ real readability metric, node-verified.
The two texts are interpolated for the demo; the formula and its ranking are exact. Flesch measures SURFACE difficulty (lengths), not conceptual difficulty — a text of short simple words can still say something hard.