Readability Score Checker
Check Flesch, Gunning Fog, SMOG grade instantly.
Paste any text to instantly see four readability scores plus word and sentence stats. All calculations run in your browser — no data is sent anywhere.
Readability Formulas Explained
Flesch Reading Ease & FK Grade Level
Flesch Reading Ease scores text from 0 (very hard) to 100 (very easy). A score of 70–80 is plain English suitable for most audiences. The Flesch-Kincaid Grade Level converts the same inputs into a US school grade — a score of 8 means an 8th-grader can comfortably read it. Both formulas use average sentence length and average syllables per word.
Gunning Fog Index
The Gunning Fog Index estimates the years of formal education a reader needs to understand a text on the first pass. It penalizes long sentences and words of three or more syllables (complex words). Most popular magazines target a Fog score of 8–10. Business writing ideally sits below 12.
SMOG Grade — Use Cases
SMOG (Simple Measure of Gobbledygook) is widely used for health and patient-facing documents. It counts polysyllabic words across 30 sentences and estimates comprehension grade level. Use these scores together when writing blog posts, marketing copy, legal disclosures, or UX microcopy to match the reading level of your target audience.
Flesch = 206.835 − 1.015×(words/sentences) − 84.6×(syllables/words) Flesch Reading Ease — Score Guide
| Score Range | Difficulty | Typical Audience |
|---|---|---|
| 90 – 100 | Very Easy | 5th grade |
| 80 – 90 | Easy | 6th grade |
| 70 – 80 | Fairly Easy | 7th grade |
| 60 – 70 | Standard | 8th–9th grade |
| 50 – 60 | Fairly Difficult | 10th–12th grade |
| 30 – 50 | Difficult | College level |
| 0 – 30 | Very Difficult | College graduate |
Frequently Asked Questions
What is a good Flesch Reading Ease score?
A score of 60–70 is considered standard for general audiences. Scores above 70 are easy to read (think popular novels or blog posts). Scores below 30 are very hard and suit academic or technical writing.
How is the FK Grade Level different from Flesch Reading Ease?
They use the same two variables — average sentence length and syllables per word — but produce different outputs. Flesch gives a 0–100 ease score (higher = easier), while FK Grade Level gives a US school grade (higher = harder).
How many sentences do I need for an accurate SMOG score?
SMOG is most accurate with at least 30 sentences. For shorter texts the tool still calculates a score, but treat it as an estimate. If your text has fewer than 30 sentences, Flesch and Gunning Fog are more reliable guides.
What counts as a complex word in Gunning Fog?
Any word with three or more syllables is counted as complex. Proper nouns and compound words that happen to be long can inflate the score, so Fog works best for prose-heavy content like articles and reports.
Does this tool send my text to a server?
No. All four readability calculations run entirely in your browser using JavaScript. Your text is never uploaded or stored anywhere.
What is the formula for Flesch Reading Ease?
Flesch Reading Ease = 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words). A higher result means easier text.