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ATOS Analyzer

renaissance.com

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Spec score 8.4 #5 of 25 in Readability Checkers

What it is

ATOS Analyzer is a free web tool for estimating the readability level of text and books in English or Spanish. Users can enter a passage, analyze an entire book, or submit a sample with an estimated word count. Text can be typed or uploaded as a .txt, .docx, or .epub file, with uploads limited to 10 MB. The suggested passage length is 150 to 25,000 characters. Results include an ATOS level, grade-level equivalent, word count, AR Points, average word length, average sentence length, and language. ATOS estimates complexity on a grade-level scale using sentence length, word length, and word difficulty; its measure also accounts for book length. For a sampled book, Renaissance recommends three passages of about 150 words from different parts and an estimated total word count. Scanned documents need OCR to become recognized text before submission; changing a file extension does not convert them. The page includes a CCSS/ATOS grade-band chart for grades 1 through 12. Renaissance presents the measure as guidance for matching students with appropriately leveled reading material.

Spec sheet

Purpose
The analyzer calculates readability levels for text passages or books.Read 8 Oct 2026 · renaissance.com
Intended users
Renaissance describes ATOS as a readability measure designed to guide students to appropriate-level books.Read 8 Oct 2026 · gestest.renaissance.com
Audience
Renaissance describes ATOS as a way to identify the difficulty level of written materials and compare it with students’ reading ranges in classes.Read 8 Oct 2026 · uk.renaissance.com
Security
Renaissance says it implements and continuously improves physical, technical, and administrative safeguards for information security and data privacy.Read 8 Oct 2026 · renaissance.com
Support
Renaissance offers product support through its Knowledge Base, support form, in-product chat, phone during regular business hours, and email.Read 8 Oct 2026 · renaissance.com
Founded
1986Read 28 Sep 2026 · renaissance.com
Analysis modes
Users can analyze a text passage, an entire book, or a book sample with an estimated word count.Read 8 Oct 2026 · renaissance.com
Analysis types
It offers analysis for a text passage, an entire book, or a book sample with an estimated word count.Read 8 Oct 2026 · renaissance.com
ATOS factors
Renaissance says ATOS considers average sentence length, average word length, word difficulty, and book length.Read 8 Oct 2026 · gestest.renaissance.com
Book sample guidance
For a book sample with estimated word count, the page recommends three passages of approximately 150 words from different parts of the book.Read 8 Oct 2026 · renaissance.com
Book sample method
For a book analysis using a sample and estimated word count, the tool asks for three passages of approximately 150 words from different parts of the book and an estimated word count.Read 8 Oct 2026 · renaissance.com
File support
The page lists .txt, .docx, and .epub as supported file types, with a maximum upload size of 10 MB.Read 8 Oct 2026 · renaissance.com
Input options
Users can type a passage or upload a file for analysis.Read 8 Oct 2026 · renaissance.com
Input preparation
For scanned text, Renaissance says the image must be converted to recognized text with OCR; changing the file extension does not work.Read 8 Oct 2026 · renaissance.com
Instructional guidance
The analyzer page provides a CCSS/ATOS grade-band chart for instructional reading from grades 1 through 12.Read 8 Oct 2026 · renaissance.com
Languages
The tool offers English and Spanish analysis.Read 8 Oct 2026 · renaissance.com
Passage limit
The suggested minimum typed passage length is 150 characters, and the maximum is 25,000 characters.Read 8 Oct 2026 · renaissance.com
Results
Results include ATOS level, grade level equivalent, word count, AR Points, average word length, average sentence length, and language.Read 8 Oct 2026 · renaissance.com
Text complexity
ATOS uses average sentence length, average word length, and word difficulty to estimate text complexity on a grade-level scale.Read 8 Oct 2026 · renaissance.com
Text entry
Users can type or upload text for analysis.Read 8 Oct 2026 · renaissance.com
Text limit
The suggested minimum passage length is 150 characters and the maximum is 25,000 characters.Read 8 Oct 2026 · renaissance.com
Text preparation
Scanned documents must be converted to recognized text using OCR before submission.Read 8 Oct 2026 · renaissance.com

Plans and prices

ATOS Analyzer Free text passages or books · 25,000-character text limit · 10MB maximum upload Read 8 Oct 2026 · renaissance.com

Every ATOS Analyzer plan and price →

Strong points and limits

Strong points

  • Analyzes passages, full books, or book samples.
  • Supports English and Spanish analysis.
  • Accepts .txt, .docx, and .epub uploads.
  • Reports grade equivalent and ATOS level.
  • Includes a grades 1–12 reading-band chart.

Limits

  • Uploads are limited to 10 MB.
  • Passages are suggested to be 150–25,000 characters.
  • Scanned documents require OCR before submission.
  • Book samples call for three passages and an estimated word count.

Who it suits

It suits educators and readers assessing text difficulty or comparing written material with students’ reading ranges. Book analysis can use either the full book or a sample with an estimated word count.

Verdict

ATOS Analyzer provides several ways to assess reading difficulty, with results that include grade-level context and text statistics. Its passage and upload limits, plus the OCR requirement for scans, shape what users can submit.

Where Specifiction places it

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