Readability Score Checker
Paste your writing and see six readability scores at once: Flesch Reading Ease, Flesch-Kincaid grade, Gunning Fog, Coleman-Liau, SMOG and the Automated Readability Index. Each card is colour-coded and reads the score in plain language, and the sections below give the published formula behind every one. Free, no sign-up, and nothing is uploaded.
How to Use the Readability Score Checker
- Paste your text. At least a few sentences, and ideally 100 words or more. The formulas were built on samples of that size, and a single sentence swings the scores wildly.
- Check the counts. Words, sentences, average sentence and word length, syllables and complex words (three or more syllables) are shown first. Every score is built from these numbers.
- Read the six cards. Green means easy to read, yellow means moderate, and red means demanding. Grade-level scores read as US school grades.
- Edit and compare. Shorten the longest sentences and swap long words for plain ones, then watch the scores fall.
The Six Formulas
| Score | Formula | Built from |
|---|---|---|
| Flesch Reading Ease (Flesch, 1948) | 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words) | Sentence length, syllables per word. Higher is easier, 0 to 100 here. |
| Flesch-Kincaid Grade Level (Kincaid et al., 1975) | 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59 | The same two measures, expressed as a US grade. |
| Gunning Fog Index (Gunning, 1952) | 0.4 × [(words ÷ sentences) + 100 × (complex words ÷ words)] | Sentence length and the share of 3+ syllable words. |
| Coleman-Liau Index (Coleman and Liau, 1975) | 0.0588 × L − 0.296 × S − 15.8, where L is letters per 100 words and S is sentences per 100 words | Letters, not syllables, so it needs no syllable guess. |
| SMOG Index (McLaughlin, 1969) | 3 + √(polysyllable count × 30 ÷ sentences) | Words with 3+ syllables, scaled to 30 sentences. |
| Automated Readability Index (Senter and Smith, 1967) | 4.71 × (letters ÷ words) + 0.5 × (words ÷ sentences) − 21.43 | Letters per word and sentence length. |
Reading Ease is held between 0 and 100, and the Flesch-Kincaid, Coleman-Liau and ARI grades are floored at 0. A very short or very dense sample can therefore show 0 or 100, which signals that the text is outside what the formula measures.
A Worked Example
Paste this: Sleep helps the brain store what it learns during the day. Students who sleep well usually remember more and solve problems faster. Skipping sleep to study longer often backfires, because the facts that were crammed are rarely stored properly. The checker counts 39 words, 3 sentences (13.0 words each), 57 syllables, 201 letters and 3 complex words. That gives:
| Score | Result | Reading |
|---|---|---|
| Flesch Reading Ease | 70.0 (69.99 before rounding) | Yellow; plain English, a hair under the green line |
| Flesch-Kincaid Grade | 6.7 | Green; about grade 7 |
| Gunning Fog | 8.3 | Yellow |
| Coleman-Liau | 12.2 | Red; about grade 12 |
| SMOG | 8.5 | Yellow |
| Automated Readability Index | 9.3 | Yellow |
The same passage spans grade 6.7 to grade 12.2 depending on the formula, because the formulas weigh different things: Flesch-Kincaid uses syllables per word, Coleman-Liau and ARI use letters per word, and Fog and SMOG count long words. This passage has an average of 5.2 letters per word, which lifts the letter-based scores. This is normal. Pick one score, say Flesch-Kincaid, and track it as you edit rather than comparing across formulas.
Reading Ease Bands
| Flesch Reading Ease | Level | Description |
|---|---|---|
| 90–100 | 5th grade | Very easy |
| 80–90 | 6th grade | Easy |
| 70–80 | 7th grade | Fairly easy |
| 60–70 | 8th–9th grade | Plain English |
| 50–60 | 10th–12th grade | Fairly difficult |
| 30–50 | College | Difficult |
| 0–30 | College graduate | Very difficult |
Microsoft recommends that most documents land between 60 and 70 on Reading Ease and at grade 7 to 8 on Flesch-Kincaid. Academic writing for specialists often scores lower on Reading Ease, and that is acceptable if the readers are specialists. This tool's own colours turn green at 70 and above for Reading Ease and at 8 or below for the grade scores.
What This Checker Does Not Do
- Syllables are estimated. The tool counts syllables by spelling rules and a list of exceptions, the same counter as the Syllable Counter. Against a pronouncing dictionary it agrees on about 98 in 100 common English word forms, including past-tense verbs such as jumped and words such as create, poem and area. It still misjudges some words that speakers shorten, such as Wednesday or vegetable, and it counts fire and hour as one syllable. Over a whole text the errors partly cancel, but short samples can drift.
- Sentences are found by punctuation. Every full stop, exclamation mark or question mark ends a sentence. Decimals, abbreviations and web addresses add extra sentences, which pulls sentence length and grade down. Headings without punctuation merge into the next sentence.
- Gunning Fog is simplified. The published method leaves out proper nouns, familiar jargon, compounds and words that reach three syllables only through -es, -ed or -ing. This tool counts every word with three or more syllables.
- SMOG is the shortcut version. It applies 3 + √(polysyllables × 30 ÷ sentences) to whatever you paste, whereas the method calls for a sample of 30 sentences. Treat it as an estimate on short texts.
- Digits are not letters. The letter-based scores count letters only, so numbers add nothing to length.
- Surface features only. None of the formulas measure organisation, vocabulary familiarity, clarity or accuracy. A text can score as easy and still confuse the reader.
Which Tool Do You Need?
| If you want… | Use |
|---|---|
| Grade-level and ease scores | This page |
| Syllables per word or per line | Syllable Counter |
| Sentence length in detail | Sentence Counter |
| Passive sentences highlighted | Passive Voice Detector |
| Padded phrases to cut | Wordiness Checker |
| Silent reading and speaking time | Reading Time Calculator |
Frequently Asked Questions
- What is a good readability score?
- For general readers, a Flesch Reading Ease of 60 to 70 and a Flesch-Kincaid grade of about 7 to 8 are common targets, the range Microsoft suggests for most documents. Specialist and academic writing is often harder and can be appropriate if your readers expect it.
- What is the difference between Flesch Reading Ease and Flesch-Kincaid Grade Level?
- They use the same two measures, average sentence length and average syllables per word, with different weights. Reading Ease gives a 0 to 100 score where higher is easier. Grade Level converts the result into a US school grade where lower is easier. The two cannot be converted into each other exactly.
- Why do the six scores disagree?
- Each formula measures different features. Flesch scores use syllables, Coleman-Liau and ARI use letters, and Fog and SMOG count long words. A text with many long one-syllable words or very short sentences can score differently on each. Choose one score and track it over drafts.
- How do I lower my reading level?
- Shorten your longest sentences, split sentences at 'and' or 'which', and replace words of three or more syllables with plainer ones where the meaning allows. The effect is largest for sentence length, which every formula includes.
- Why is my score different in Microsoft Word?
- Word uses its own rules for finding sentences and counting syllables, and shows only Reading Ease and Flesch-Kincaid. Small differences are normal even though the formulas are the same.
- Is my text uploaded?
- No. The scores are calculated in your browser and the text is not sent or stored.