How to use GPT-5 in Microsoft 365 Copilot for Excel

TLDR: In August 2025, Microsoft rolled out GPT-5 across its Copilot ecosystem, including Microsoft 365 Copilot, the standalone Copilot app, GitHub Copilot and Azure AI Foundry. Until now, Copilot relied on separate modes: a fast model for short answers and a deeper reasoning model for complex work. GPT-5 removes that guesswork with a new Smart mode that switches automatically. GPT-5 arrives in the Copilot app with Pages, Bing and Edge integration, plus voice commands. This article explains what changed, why it matters, and how to use GPT-5 for excel.

What Copilot was before GPT-5

Earlier Copilot felt like two half-tools bolted together. If you wanted speed, you used the lightweight mode. If you wanted depth, you toggled to a slower reasoning mode. The system didn’t decide for you, and unless you understood the difference, you either stuck with one or wasted time switching.

Its view was narrow. Ask it about yesterday’s meeting, and it gave you nothing unless you pasted in the transcript. Ask it about a spreadsheet, and you had to copy data cell-by-cell. It was a tool for specific snippets, not entire workflows.

What changed with GPT-5

Smart mode now routes between fast and deep reasoning in real time. You don’t see the switch, but you feel the effect: fast answers when you need them, careful reasoning when the task is complex.

The context window expanded dramatically. Copilot can now draw on the connected layer of Microsoft Graph your Outlook threads, Teams chats, SharePoint docs and OneDrive files. That makes it capable of stitching together meaning across your work. It can detect tone shifts in emails, cross-reference proposals, and notice when two documents contradict each other.

Unlike earlier AI tiers, GPT-5 isn’t restricted to enterprise users. Microsoft pushed it into every Copilot tier. That means the same reasoning power is in Word, Outlook, Teams, the consumer Copilot app, GitHub Copilot for developers, and Azure AI Foundry for builders.

What this looks like in practice

In Outlook, GPT-5 can compress hundreds of emails into a same-day action list. Before, you had to paste the emails in or skim them yourself. Now it reads the thread directly, highlights urgent items, and flags who’s waiting on you.

In Teams, you can miss a marketing meeting and still get a clear recap. GPT-5 pulls from meeting transcripts, chats and notes, then delivers the decisions taken and the actions assigned to you. Without it, you’d be chasing colleagues for scraps of context.

In OneDrive and Excel, you can ask it to locate this year’s forecast file, compare it with last year’s, and explain the differences. That used to mean manually finding files, opening both, scanning for changes, and hoping you spotted the right cells.

For consumer users, Copilot Pages in the app lets you generate and edit content—stories, code, infographics in real time. Voice commands now tie into Bing and Edge, so you can ask for research or ideas hands-free. Free users even get more reasoning queries per day than ChatGPT’s free tier, widening access.

Why this matters

The change isn’t just about “smarter AI.” It’s about how work feels. Instead of juggling menus or toggling modes, you type naturally and let Smart mode adapt. Instead of copy-pasting files, Copilot understands your workflow and pulls what it needs.

That distinction is why Copilot differs from ChatGPT. ChatGPT only works with what you type. GPT-5 in Microsoft 365 Copilot reasons across your actual files, emails and meetings. The grounding is what turns it from a clever chatbot into a genuine work companion.

And for enterprises, nothing changes on security or compliance. Data stays inside Microsoft 365’s existing controls: DLP, retention, audit, and privacy. IT doesn’t have to rewrite governance for GPT-5.

What you can do now with MS Excel

The most immediate place you’ll notice GPT-5 at work is inside Excel. Copilot has moved from being a sidebar chatbot to acting like a real function in your spreadsheet.

Before: You typed a request into the Copilot panel: for example, “Classify this feedback as positive or negative.” Copilot spat out a list in the chat window, which you then copy-pasted into cells.

Now: You type =COPILOT("classify as positive or negative", A2) directly in cell B2. The result lands in the cell, and it updates automatically if A2 changes just like =SUM(A1:A10) recalculates when you edit numbers. Copilot has become part of Excel’s calculation engine, not just a helper off to the side.

What this unlocks and why we love it:

• Data classification: Categorise survey responses, support tickets, or customer feedback directly in your sheet.
  
• Content generation: Create summaries, SEO keywords, or alternative phrasings cell by cell.
  
• Dynamic updates: When the source data changes, the AI outputs refresh automatically. No more re-running scripts.
  
• Formula integration: Combine =COPILOT() with IF, SWITCH, or LAMBDA for workflows that mix AI with classic Excel logic.
  
• Current limits: It supports around 100 calls every 10 minutes and 300 per hour. It works with your spreadsheet data, but it doesn’t fetch live web or internal business data on its own.

FAQs

Q: Do I need to turn something on to use GPT-5?
A: No. If Copilot appears in your Microsoft 365 apps, GPT-5 is already active.

Q: How do I know it’s using my files or meetings?
A: Ask it directly. For example: “Use my OneDrive forecast file and last year’s version to show the differences.” If it cites the right files or meetings, it’s grounded.

Q: Can it replace me reading everything?
A: No. Think of it as a filter, not a replacement. It cuts 200 emails down to 10, or a one-hour meeting down to a two-minute recap. But you still need to sense-check.

Q: What’s the main difference from ChatGPT?
A: ChatGPT answers what you type. Copilot with GPT-5 can see your Outlook, Teams, and OneDrive data, so it answers in the context of your actual work. But you will need to prep it properly and learn to prompt with intent.

 Our view is that GPT-5 makes Copilot even more useful. The guesswork about which mode to use is gone. The hours lost to inboxes, missed meetings, and messy files start shrinking. That’s the real move here: from typing at an AI chat interface to working with one.

If you want more than a surface skim, join the 5-Day AI Bootcamp. In one week we show you exactly how to use tools like GPT-5 in Copilot against your own workload. By Friday, you’ll have live examples running inboxes condensed, meetings summarised, and documents analysed.