Two scores, one set of inputs
Both formulas were developed by Rudolf Flesch in the 1940s (the grade-level version later adapted by J. Peter Kincaid for the U.S. Navy) and both use the same three raw counts — words, sentences, and syllables — combined differently:
- Flesch Reading Ease:
206.835 − 1.015 × (words / sentences) − 84.6 × (syllables / words)— a 0–100 scale where higher means easier to read. - Flesch-Kincaid Grade Level:
0.39 × (words / sentences) + 11.8 × (syllables / words) − 15.59— outputs a number matching a U.S. school grade level.
Both formulas are driven by exactly two things: how long your sentences are, and how many syllables your words have. That's a deliberate simplification — they say nothing about whether your writing is well-organized, accurate, or engaging. A score is a proxy for "hard to parse," not a proxy for "good."
How to read the numbers
| Reading Ease | Grade Level | Description |
|---|---|---|
| 90–100 | ~5th grade | Very easy — comics, simple instructions |
| 60–70 | ~8th–9th grade | Standard — most news writing, general web content |
| 30–50 | College level | Difficult — academic papers, legal text |
| 0–30 | Graduate level | Very difficult — dense technical or legal writing |
For general web content and marketing copy, most style guides (including Google's own writing guidelines and the U.S. government's Plain Writing Act) target a Reading Ease around 60–70 — roughly an 8th-to-9th-grade level. That's not a comment on the reader's intelligence; even highly educated readers process shorter sentences faster, especially when skimming.
Why syllable counting is always approximate
No readability tool — this one included — has access to a full pronunciation dictionary. Syllable counts are estimated by counting vowel-sound groups in each word, with a few adjustments for silent endings. This gets the vast majority of common English words right, but it's an estimate, not a lookup, so scores from different tools on the same text can differ by a point or two. Treat the number as directional, not exact.
Concrete ways to lower your grade level
Since the formulas only respond to sentence length and word complexity, the fixes are mechanical:
- Split long sentences. A 30-word sentence with two ideas usually reads better as two 15-word sentences with one idea each.
- Cut subordinate clauses. "Which," "that," and "although" clauses are often removable without losing meaning.
- Prefer short, common words. "Use" over "utilize," "help" over "facilitate," "before" over "prior to."
- Avoid stacked noun phrases. "The system configuration update process" is harder to parse than "updating the system configuration."
- Read it out loud. Sentences that are hard to say in one breath are usually hard to read, too — this catches issues the formula misses.
When a high grade level is fine
Not everything should aim for 8th grade. Legal disclaimers, academic writing, and technical documentation for an expert audience routinely — and appropriately — score in the "difficult" range, because precision matters more than accessibility for that specific reader. Use the score as a check against your intended audience, not as a universal target.