Readability Score Calculator: Flesch-Kincaid, Gunning Fog, SMOG and More

What is a readability score?

A readability score estimates how easy a text is to read, based on measurable features such as sentence length and word length. Short sentences and short words make text easier. Long sentences full of long words make it harder. Scores do not judge whether your writing is good or true, but they are a fast, objective way to check that it matches the people who will read it.

Writers use readability scores to make web pages, instructions, product descriptions, emails and school materials clearer. Many style guides for public information recommend plain language, and a commonly cited target for general web content is around the 7th to 9th grade level.

How to use the readability calculator

1. Paste your text into the box. A few full paragraphs give the most reliable result.
2. Read the Flesch Reading Ease score and the average grade level in the summary.
3. Check the table of six tests to see how they agree or differ.
4. Look at the longest sentences. Splitting a very long sentence is the quickest way to improve a score.
5. Edit your text and watch the scores update as you type.

The six readability tests explained

• Flesch Reading Ease (Rudolf Flesch, 1948): a score from about 0 to 100, where higher means easier. It uses average sentence length and syllables per word.
• Flesch-Kincaid Grade Level: converts the same inputs into a US school grade, such as 8.2 for early 8th grade.
• Gunning Fog Index: estimates the years of education needed, using sentence length and the share of words with three or more syllables.
• SMOG Index: counts complex words in sentences and is considered most reliable on texts of 30 sentences or more.
• Coleman-Liau Index: uses letters per word and sentences per 100 words, so it does not need syllable counts.
• Automated Readability Index (ARI): uses characters per word and words per sentence.

How to make your writing easier to read

• Keep most sentences under 20 words and split any that run past 25.
• Choose short, common words: use instead of utilize, and help instead of facilitate.
• Prefer the active voice: the team fixed the bug is clearer than the bug was fixed by the team.
• Use headings, short paragraphs and lists so readers can scan.
• Define technical terms the first time you use them, and avoid stacking several in one sentence.

Limits of readability formulas

Readability formulas are built for English and rely on a rule-based syllable count, so results can differ by a point or two between tools. They cannot judge clarity, structure, tone or accuracy, and they can be fooled: a text made of short nonsense words scores as easy. Use the numbers as a guide, read your text aloud, and when it matters, test it with real readers.

Example: simplifying a sentence

Original: Individuals who wish to terminate their subscription are required to submit a written request prior to the commencement of the next billing period. That sentence is 23 words and scores around grade 13, which is college level. Rewrite: To cancel your subscription, send us a written request before your next billing date. It is 14 words and scores around grade 8. The meaning is the same, but the second version is quicker to read, easier to scan on a phone and easier for readers who are not native English speakers.

Run both versions through the calculator and compare the Flesch score and the grade level. Small edits to the longest sentences usually have the biggest effect.

Flesch Reading Ease score guide

Frequently Asked Questions