ValleyFill

Free tool

Plain language and reading level checker

Paste English text to see an estimated reading grade and a list of long sentences. The check runs in your browser. We do not upload or store what you paste.

Tool inputs and agreement

A few paragraphs of body text work best. Headings, menus and labels count as short sentences and can make a page look easier to read than its body text.

This tool runs in your browser. The text you enter and the result stay on your device; this tool does not send them to ValleyFill or an AI provider. For Terms acceptance, we store only the acceptance time, tool path and Terms version in this tab’s session storage; that record is not sent to ValleyFill. Accessibility display preferences are stored separately in your browser. Normal page requests still reach our host, and our Privacy Policy describes server logs and anonymous visit counts. Don’t paste passwords or sensitive personal information. This is a free automated tool, not legal advice, certification or a guarantee of accessibility or compliance.

What the scores are

This page reports two well-known formulas from Kincaid, Fishburne, Rogers and Chissom (1975): Flesch Reading Ease and the Flesch–Kincaid Grade Level. They use sentence length and an estimate of syllables per word. They are a writing aid, not a measurement of whether a person will understand you. Source: the 1975 Naval Technical Training Command report (PDF).

We count syllables with a short vowel-group rule, not a dictionary, so another checker can disagree by a fraction of a grade. The formulas were built for English.

How this page counts: a sentence ends at a full stop, question mark or exclamation mark followed by a space or the end of the text, and a piece with no letters is not a sentence. A word is a run of letters (apostrophes inside a word are kept) or a run of digits. Syllables are the groups of vowels (a, e, i, o, u, y) in each word, minus one for a final silent “e”, with at least one syllable per word.

How this relates to WCAG

WCAG 2.1 Success Criterion 3.1.5 Reading Level (Level AAA) says that when text requires reading ability more advanced than the lower secondary education level — after removing proper names and titles — you should also provide supplemental content or a simpler version. WCAG defines lower secondary education as the period that ends nine years after the start of primary education, following the UNESCO International Standard Classification of Education. Source: Understanding Success Criterion 3.1.5.

This tool treats an estimated Flesch–Kincaid grade above 9 as a signal to consider a summary, a diagram, or a simpler version. That is an approximation of “lower secondary,” not a WCAG test method. The success criterion itself does not name Flesch–Kincaid. We also do not strip proper names and titles, which 3.1.5 allows you to ignore.

How this relates to Title II

ADA Title II web rules for state and local government point at WCAG 2.1 Level AA, not AAA. Success Criterion 3.1.5 is AAA, so a high grade level on this page is not, by itself, a Title II failure. It is still useful: clearer sentences help more people, including people with cognitive and reading disabilities, which is the reason 3.1.5 exists. Sources: ADA.gov fact sheet on the 2024 web rule and Understanding 3.1.5. This is general information, not legal advice.

Tips that usually help

The U.S. federal plain-language guidelines suggest writing for your reader, using common words, short sentences, and lists where they fit, and explaining terms the first time you use them. Those are writing practices, not WCAG pass/fail tests. Source: plainlanguage.gov guidelines.

What this tool cannot do

It does not fetch a URL, check a whole website, or replace an accessibility audit. It does not evaluate headings, images, forms, keyboard access, color, or PDFs. Use our color contrast checker for text and background colors, or a Title II Snapshot for basic signals on a public website.

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