Last updated 07-17-2026
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Three Sigma
Three Sigma is a document research assistant that answers questions across the files you upload. Point it at PDFs, Word documents, or PowerPoint decks and ask follow-ups in plain language instead of skimming page by page.
What sets it apart is transparency. When you ask a question, Three Sigma shows how it reached the answer rather than hiding the reasoning behind a black box. You can also query entire folders at once, which helps when a project spans annual reports, spreadsheets, and slide decks.
It is built for people who live in long documents: analysts reviewing filings, researchers pulling facts from reports, and teams that need quick, traceable answers from their own files. A ChatGPT plugin and a solo chat mode extend the same workflow into OpenAI and everyday Q&A.
Shows how each answer was reached so you can verify the reasoning
Ask questions across whole folders of PDFs, Word docs, and PowerPoints
All plans include a ChatGPT plugin for users with an OpenAI account
Free solo mode works like ChatGPT when you have no document to upload
Supports PDFs, Word files, and PowerPoint decks up to about 1,000 pages
Runs multiple models to improve reliability on harder research questions
Answers include visibility into how Three Sigma reached each conclusion.
Lets you question entire folders of documents instead of one file at a time.
Includes a ChatGPT plugin on all plans for users with existing OpenAI accounts.
Offers encrypted storage with access limited to your account.
Search across documents is still marked coming soon on the pricing page.
Table and chart references in documents are listed as a coming soon feature.
Upload support is limited to PDF, Word, and PowerPoint formats.
No dedicated mobile app is mentioned on the site.
What file types does Three Sigma support?
Three Sigma supports PDFs, Word documents, and PowerPoint presentations. The pricing page also notes that search across documents is coming soon.
Does Three Sigma offer a free trial?
Yes. Three Sigma's Standard plan includes a Start Free Trial option on the pricing page, so you can test uploads and questions before committing to a paid plan.
How much does Three Sigma cost?
Three Sigma's Standard plan is listed at $14 per month on the pricing page. The plan includes 750 pages of uploads per month at the default slider setting, with higher page limits available by adjusting usage.
Is my data private on Three Sigma?
Three Sigma states that uploaded data is fully encrypted and stored in a location accessible only to you. Its privacy policy lists [email protected] for privacy questions.
Does Three Sigma have a ChatGPT plugin?
Yes. Three Sigma includes access to its ChatGPT plugin on all plans if you already have a ChatGPT account. Plugin usage is listed as unlimited questions.
What is the maximum document length on Three Sigma?
Three Sigma's pricing FAQ says documents can be up to 1,000 pages today, while the Standard plan listing mentions support for files with up to 750 pages. The site notes it is working to raise the limit.
Can I use Three Sigma without uploading a document?
Yes. Three Sigma offers free solo mode, which lets you start a thread without referencing a document, similar to a general chat assistant.