AI in Spreadsheets: What Copilot, Gemini and Claude Actually Do in Your Cells

There is a version of "AI in spreadsheets" that the demos show — type a question, get a chart — and a version that survives contact with a real workbook. We spent a month with the second version across Excel and Google Sheets, and the most useful thing we learnt is where each vendor draws its own line. All three publish a list of things not to use their tool for, and the lists are more honest than the marketing.

The other thing we learnt is that the category is moving under our feet. Excel's in-cell COPILOT function, the feature that made the biggest splash a year ago, is withdrawn from today.

Excel: the function goes, the side pane stays

Microsoft's COPILOT function let you write =COPILOT("classify this feedback", A2) and get a model's answer in the cell. It was rate-limited to 100 calls every ten minutes, needed a Copilot add-on licence on a work account or Microsoft 365 Premium on a personal one, and its own support page listed what to avoid: numerical calculations, and anything with legal, regulatory or compliance implications. It also only saw the prompt and the cells you passed it, nothing else in the workbook.

That same page now carries the notice: starting 14 September 2026, the COPILOT function will no longer be available, and Copilot in Excel — the side pane — is where the same tasks live. If you built anything on the function, paste its outputs as values this week. The pane does the useful things the function did: generate a formula from a description, summarise a range, suggest a chart, and it can see the sheet, which the function could not. What it does not do is sit in a cell and recalculate, and honestly that was the part people misused.

Every vendor's documentation says the same thing in different words: use the assistant for text and explanation, not for the number that goes on the invoice.

Google Sheets: the AI function that can read the web

Google's equivalent is still in the cell and, for the tasks it suits, is the most useful in-cell tool we tried. The syntax is =AI("prompt", [range]) — you can also type =Gemini() — and the help page lists what it does: generate text, summarise, categorise, and analyse sentiment across the range you point it at. The feature that separates it from Excel's withdrawn function is that it can access real-time information from Google Search, so a column of company names can become a column of headquarters cities without leaving the sheet.

The limits are practical. You select cells and click Generate; only the first 350 selected cells run at a time, there are short-term and long-term generation limits, and the output is text you can refresh rather than a live formula. You need an eligible Google Workspace or Google AI plan. And the help page is plain that Gemini features may suggest inaccurate or inappropriate information and are not a substitute for professional advice. That is the right frame: it is a fast first draft of a column, to be spot-checked, not a lookup.

Where it shines is the messy middle of a spreadsheet — the column of free-text survey answers that needs sorting into five themes, the list of job titles that needs a seniority level, the product descriptions that need a one-line summary. Those are the tasks nobody wanted to write a formula for, and they are exactly what a language model is good at.

Claude for Excel: for the model you inherited

Claude for Excel is a different kind of tool. It is an add-in from Microsoft AppSource, available on Claude Pro, Max, Team and Enterprise plans, and it runs on Excel for the web, Windows and Mac. Rather than living in a cell, it reads the workbook and talks about it, and the feature that makes it worth the licence is that its answers come with cell-level citations you can click. Ask how the revenue figure in C42 is derived and you get the chain of assumptions with references, not a paragraph.

It edits, too, and this is where it is most careful: change a discount rate and it updates the value while keeping formula relationships intact so downstream cells recompute; ask it to find the source of a #REF! error and it traces it; it can populate a template, build a three-statement model from a trial balance, and do native Excel operations like sorting, pivot tables and conditional formatting. It does not touch data tables, macros or VBA, and it will not run on the perpetual-licence Excel 2016 and 2019, on iPad or on Android.

Anthropic's list of what not to do is the most explicit of the three. It is not recommended for final client deliverables without human review, audit-critical calculations without verification, or highly sensitive data without proper controls. And there is a warning that the other two do not spell out as clearly: a spreadsheet from outside your organisation can contain hidden instructions — a prompt injection — that tries to make the add-in extract data or change records, so only use it on trusted files and read the confirmation prompts. We wrote about the same risk in browsers in our piece on browser agents; it applies to any assistant that can act on a document you did not write.

Side by side

	Where it lives	What it needs	Best at	Vendor says not for
Copilot in Excel	Side pane (in-cell function withdrawn 14 Sept 2026)	Copilot add-on or Microsoft 365 Premium	Formulas from a description, charts, summaries	Numerical calculations; legal, regulatory or compliance work
AI function in Sheets	In the cell	Eligible Workspace or Google AI plan	Categorising and summarising text columns, filling facts from Search	Anything relied on as professional advice
Claude for Excel	Add-in side pane	Claude Pro, Max, Team or Enterprise	Explaining and safely editing models, debugging errors	Final deliverables and audit-critical figures without review

The rule we ended up with

AI goes in the text columns and stays out of the number columns. Let it categorise, summarise, extract, explain and find the broken reference. Do not let it produce the figure that the decision rests on, because a model that is non-deterministic by design should not be the thing that calculates a margin, and every vendor here says the same in its own documentation.

That rule also answers the licence question. If your spreadsheet work is lists — contacts, feedback, inventory descriptions — Google's AI function or whichever Copilot licence you already hold is enough, and the question is mostly which suite you are in. If it is models, Claude for Excel is the one that understands the workbook as a structure rather than a grid, and that is worth a Pro plan on its own. And if the spreadsheet has quietly become something else, the point at which it should be a database is a separate question that AI in the cells does not answer — it just makes the spreadsheet last longer than it should.