Readability Calculator
Flesch reading ease and grade level from pasted text.
What it does
Reading formulas turn style into numbers from two averages: words per sentence and syllables per word. The pangram pair default lands at ease 93.7 with grade 2.3 across 17 words and 2 sentences. The tool above scores any pasted paragraph the same way.
The math dates to Navy research on training manuals. Reading ease starts at 206.835 and subtracts for long sentences and heavy words, while grade level rebuilds those averages into school years. Dense prose can slide below zero ease or past college grades without breaking either scale.
The original 1975 report derived the formulas from hundreds of enlisted readers, and education indexes catalog them since as the standard classroom yardsticks. Bands translate scores for planning: 90s read at grade 5, 60s at grades 8 to 9, 30s at college.
Syllable counting is the honest weak link. Estimators group vowels, trim silent endings, and miss dictionary edge cases, so treat scores as guidance for revision rather than verdicts on readers. Shorten sentences first; that lever moves both numbers fastest.
How to use
- Paste the paragraph to score.
- Keep sentence punctuation in place.
- Read ease first for plain language checks.
- Read grade for audience matching.
- Revise long sentences and retry.
Formula
- WPS
- Words per sentence.
- SPW
- Syllables per word.
- bands
- 90s grade 5 down to 30s college.
Flesch and Flesch-Kincaid pair from Navy report derivations. Syllables estimated by vowel groups; dictionary counts may differ slightly.
Worked example
Example: two pangrams
Default text scores 17 words, 2 sentences, 21 syllables.
- Averages: 17/2 = 8.5 words a sentence, 21/17 = 1.235 syllables a word.
- Ease: 206.835 - 1.015x8.5 - 84.6x1.235 = 93.7.
- Grade: 0.39x8.5 + 11.8x1.235 - 15.59 = 2.3.
- Bands: 93.7 sits in the 90s, grade 5 zone.
- Tool shows 93.7, Grade 2.3 (Grade 5), 17 words, 2 sentences.
Reference table
| Ease | Feel | Grade |
|---|---|---|
| 90 to 100 | Very easy | Grade 5 |
| 60 to 69 | Standard | Grades 8-9 |
| 50 to 59 | Fairly hard | Grades 10-12 |
| 30 to 49 | Difficult | College |
Limits
- English prose only; formulas assume it.
- Syllables estimated, not dictionary exact.
- Short samples swing on one sentence.
- Guidance for revision, not reader verdicts.
Common mistakes
- Scoring text without punctuation.
- Chasing grade alone while ease lags.
- Trusting tiny samples.
- Gaming syllables with abbreviations.
- Ignoring audience while polishing scores.
Try it yourself
Quick checks. Answers sit tucked under each question.
Two pet sentences sample?
13 words, 2 sentences: ease 96.1, grade 1.5.
Library sentence sample?
10 words, 1 sentence: ease 61.3, grade 7.2.
Which lever moves fastest?
Shorter sentences shift both scores most.
Questions
Sample score here?
93.7 ease, grade 2.3.
Higher ease better?
Yes. Higher means easier reading.
What grade for the public?
Grades 8 to 9 suit general audiences.
Why two numbers?
Ease is a 0-100 scale; grade maps to school years.
Can ease go negative?
Yes on very dense prose.
Syllables exact?
Estimated by vowel groups; close, not dictionary.