Copilot vs ChatGPT for Office Work: Plans and Fit

Which fits your existing office workflow?

Copilot has a documented fit when you need to edit Excel workbooks directly; ChatGPT is an option when you can supply text and transfer a reviewed answer back into your work. For email, documents and meetings, the facts verified here do not support a recommendation based on specific Outlook, Word or Teams integrations.

Start with the task you repeat, the information it requires and your organization’s approved tools. A formula explanation and a workbook edit are different jobs. So are drafting from supplied notes and retrieving information from a meeting system. Check the exact feature and subscription before paying.

Model names alone will not settle the choice. Microsoft’s documentation checked 2026-10-19 lists Auto as the default router in Copilot Cowork, selecting from models the organization enables. Available choices include GPT 6 Astra and Claude Fable 5.1; the latter requires the tenant to enable the Anthropic subprocessor. This does not establish which model handles a particular office task.

OpenAI’s system card dated 2026-10-07 says GPT-6 launched across free and paid ChatGPT plans globally, replacing GPT-5.6 Sol and GPT-5.6 Luna. The default variant for each plan is not verified. GPT-6.1 Sol is listed for Work and Codex, not Chat, with rollout to Plus, Pro, Business, Enterprise and Edu.

For separate product guidance, read Copilot for Professionals and ChatGPT for Professionals.

What do the plans cost?

Microsoft 365 Premium costs $19.99 per month and ChatGPT Plus costs $20 per month, but that price similarity does not establish equivalent features. A team-cost comparison remains incomplete because ChatGPT Business and Enterprise prices were not verified.

Prices and plans checked 2026-10-19. USD list prices shown to a US visitor, excluding tax; the Microsoft promotion is labeled separately.

ChatGPT prices and plans checked 2026-10-19. USD list prices, excluding tax.

Distinguish an add-on from a bundle when calculating costs. Also distinguish monthly payment from a monthly commitment: the enterprise add-on’s $31.50 payment still carries an annual commitment. The Copilot Business $18 promotion applies only to the first year; its annual-billing list price is $21.

Readers in the UK, Australia and India should check local prices, taxes and rules, which differ; the figures here are US-dollar prices only.

Where does each fit in everyday office tasks?

Excel is the clearest documented distinction: Copilot can edit workbooks with Excel’s own tools. For other tasks, the table gives generic prompting workflows, not verified app integrations or performance results.

Office-task documentation checked 2026-10-20; plan and model information checked 2026-10-19.

In Excel, open Copilot using the lower-right icon. Edit mode, the default, changes the workbook directly. Plan mode proposes a plan for review before editing. Chat mode answers without changing the workbook. After a prompt, Copilot creates a step-by-step plan; you can watch changes live and use Stop to halt them.

Windows, Mac and web support all three modes. iPad supports chat and plan, with edit rolling out; iPhone supports chat, with edit rolling out; Android supports chat. If Copilot is missing, Microsoft says your subscription may not include it or your organization may have disabled it.

For a classification task, select plan mode before using this prompt. Use synthetic or approved data and check the proposed rules before authorizing changes.

In sheet [SHEET NAME], classify entries in [SOURCE COLUMN AND RANGE] using these categories: [CATEGORIES AND DEFINITIONS].

Propose results in a new column named [RESULT COLUMN NAME]. Preserve existing values. Flag ambiguous entries rather than guessing.

Show the classification rules and proposed steps before editing. Wait for my confirmation.

For a client-email draft, use a sanitized thread. Ask for missing information separately so it does not quietly become a commitment in the reply.

Help a [PROFESSION] in [JURISDICTION] draft a reply to the supplied email thread.

Keep the draft within [WORD LIMIT] words. Answer only questions actually asked. Do not invent deadlines, fees, legal positions or promises.

After the draft, list source facts, assumptions and questions that need clarification separately.

[SANITIZED THREAD WITH CONFIDENTIAL DETAILS REPLACED BY PLACEHOLDERS]

Find more examples in our prompt library for accountants. The guides for sales managers and construction managers address profession-specific workflows and review needs.

What does our October 2026 round tell you?

Our October 2026 round provides evidence about model instruction-following, not a Copilot-versus-ChatGPT application ranking. Copilot was not in the round, and no Excel task was included. A separate round of 10 Excel and Microsoft 365 prompts on 2026-10-20 tested all five chat models answering in text, with formulas judged on logic and stated result but not executed in Excel; this was not Copilot in Excel or Microsoft 365, which remains untested.

In our October 2026 round, GPT-6 Astra passed 99% of rubric criteria on average on English prompts; 86 of 90 runs met every criterion. These were API calls through a command-line harness with tools, web and memory off, not consumer-app sessions, so app results may differ. Judges were not equally strict: part of the Claude-versus-GPT gap comes from the grader, not the model, and the scores do not establish an overall winner. Claude Fable 5.1 and Gemini 4 Argon, added on 2026-10-20 with the same prompts and rubrics and graded by GPT-6 Astra, passed 90% and 92% of criteria on English prompts, respectively; all criteria were met in 54 of 90 runs for Fable and 60 of 90 for Gemini. Gemini ran through Google’s Antigravity CLI with a tool-less agent, not the Gemini app, so app results may differ.

The round dated 2026-10-19 used 40 prompts, including 30 English and 10 Spanish prompts, across 10 professions. Each prompt had 5 pre-written rubric criteria and 3 runs per model, for 360 runs. The participating models were GPT-6 Astra, Claude Opus 5.5 and Claude Sonnet 5.

GPT outputs were graded by Claude Opus 5.5; Claude outputs by GPT-6 Astra. In that October 2026 API round’s calibration, both judges passed 97% of criteria on 30 sampled GPT runs. For 30 sampled Claude runs, the published judge passed 93%, versus 98% under the swapped judge. An editor agent, not a human, independently reread 20 verdicts and agreed with 18. For the two models added on 2026-10-20, smaller samples of 10 runs each showed the published judge passing 88% versus 100% under the swapped judge for Claude Fable 5.1, and 92% versus 98% for Gemini 4 Argon.

Most lost criteria in the October 2026 round involved added content, such as a warning, date, benefit or legal assumption absent from the input; word limits also cost the Claude models points. Review drafts for unsupported additions, even when they read smoothly. A model’s successful rubric result is not professional sign-off.

On the 6 Excel prompts within the separate round of 10 Excel/Microsoft 365 prompts on 2026-10-20, Gemini 4 Argon passed 97% of criteria, Claude Opus 5.5 96%, Claude Fable 5.1 92% and Claude Sonnet 5 83%, all graded by GPT-6 Astra; GPT-6 Astra passed 87% under Claude Opus 5.5, so its raw score is not directly comparable. The chat models answered in text, with formulas judged on logic and stated result but not executed in Excel; this was not Copilot in Excel or Microsoft 365, which remains untested, and the tested Excel prompts are listed on our Excel tool page.

Can you use confidential client data?

Organizational Copilot has documented contractual protections; ChatGPT’s data terms and Copilot’s consumer-plan terms were not verified for this page. Read your plan’s terms and your professional confidentiality requirements before supplying client, patient or employee information.

Microsoft Learn states that organizational Copilot and Copilot Chat use is covered by the Microsoft Products and Services Data Protection Addendum and Product Terms, with Microsoft acting as data processor. Prompts and responses receive the same contractual protections as Exchange email and SharePoint files.

The documentation also states encryption at rest and in transit; respect for organizational permissions, sensitivity labels, retention policies and audit; and no use of prompts, responses or Microsoft Graph data to train foundation models. Web search is a distinct condition: queries go to Bing, whose data-handling practices are separate and for which Microsoft acts as an independent controller.

Do not extend those statements to consumer subscriptions. We have not verified equivalent terms for Microsoft 365 Personal, Family, Premium or Pro, or OpenAI’s retention, training or business-protection terms for ChatGPT plans. Organizational protections also do not establish that a particular disclosure is permitted.

Limits: This is not legal, medical or tax advice. In the United States, HIPAA Privacy Rule 45 CFR 164.502(e) permits a covered entity to disclose protected health information to a business associate only with satisfactory assurance, through a business associate agreement, that it will safeguard the information. An AI vendor receiving PHI is a business associate. Confirm the agreement for your specific plan with the vendor and counsel.

Have a licensed professional in your jurisdiction review applicable confidentiality obligations and proposed data use. The professional responsible for the work must check figures, formulas and legal positions before relying on them. The guide for accountants provides further context for that review.

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