Readability Curve: Flesch-Kincaid Score & Grade Level (2D)

Your Text

Words per sentence 18

Syllables per word 1.50

Jargon density 10%

Audience literacy (grade) 8

Readability

—

Flesch Reading Ease

0.0

F-K Grade Level

0.0

Effective grade (+jargon)

0.0

Est. audience retained

How it works

Two Rudolf Flesch / J. Peter Kincaid formulas, still used by word processors and government style guides, turn plain sentence statistics into a readability estimate:

FRE   = 206.835 − 1.015·(words/sentence) − 84.6·(syllables/word)
Grade = 0.39·(words/sentence) + 11.8·(syllables/word) − 15.59

FRE runs roughly 0–100 (higher = easier); Grade estimates the US school grade a reader needs to follow the text on a first pass. Jargon density adds an extra effective-grade penalty here (dense terminology raises the bar beyond what plain syllable-counting captures).

This 2D companion plots retention directly as a curve over reader literacy grade (4–20) instead of animating a 3D crowd: at every grade level x, the curve height is the fraction of a normally-distributed population (σ≈2.2) centred on x whose literacy meets or exceeds the text's effective grade — the same statistical model as the 3D version's per-reader pass/fail check, aggregated into a continuous line instead of 160 discrete walkers. A marker on the curve tracks the "audience literacy" slider so you can read off retention for your chosen crowd directly.

Words / sentence & Syllables / word — plug straight into both formulas.
Jargon density — undefined specialised terms; up to +4.0 grade levels at 100%.
Audience literacy — the mean grade level of your actual readers; widen the gap to the text's grade and watch the marked point on the curve collapse toward zero.

Retention curve vs. reader grade Your audience (marker) Text's effective grade line