Most of the AI advice for spreadsheets still involves copying cells into a chat window, pasting an answer back, and hoping nothing broke. That is over. Claude is an add-in now: a side panel inside Excel and PowerPoint that can see the file you have open, change it directly, and show you exactly which cells it touched. Ask why a number is what it is and it answers with a citation you can click to jump to the cell. Ask it to fix the error on the summary tab and it finds the cause, fixes it, and tells you what it did.
It is on every paid Claude plan, it runs on Excel and PowerPoint on Windows, Mac and the web, and it takes about five minutes to install. Here's the install, the five jobs I would hand it first, and the honest list of what it cannot do, because there are a few.
The plan · 20 minutes, 5 prompts
Before you start
A paid Claude plan
Pro, Max, Team or Enterprise. The free plan can still make spreadsheets and decks in the normal chat as downloadable files, just not inside Office.
A Microsoft 365 subscription
Excel and PowerPoint on the web, or the Windows and Mac desktop apps kept up to date. The one-time-purchase Office 2016 and 2019 do not work, and neither does the iPad app.
A copy of the file
work on a duplicate the first few times, because it makes real changes to real cells.
Install it once
Search Microsoft AppSource for "Claude for Microsoft 365" and click Get it now. One listing covers Excel, Word and PowerPoint. Then open Excel, find Add-ins on the Home tab (on a Mac it is under Tools, then Add-ins), open Claude, and sign in with the same Claude account you use everywhere else. A side panel appears on the right, and that is the whole setup. Do the same once in PowerPoint and it is there too.
One setting worth knowing about: in the panel's settings there is a switch called "Let Claude work across files." On Pro and Max it is on by default, and it is what lets Claude pull numbers from an open Excel file into an open PowerPoint deck. There is also an Instructions box in the settings where you can type standing rules like "always format numbers with thousand separators" and it applies them every time.
Rick's tip
Only open files you trust with the add-in on. A spreadsheet from a stranger can contain hidden text that tries to give Claude instructions, and Anthropic's own docs warn about it. Claude asks before anything risky, but "trusted files only" is the rule.
Let it read and explain your spreadsheet
The first job is the one that makes people get it: hand it a spreadsheet someone else built and ask what is going on. Every answer comes with cell references you can click, so you are never taking its word for it.
Then the clean-up, which is the job everyone hates and Claude does in about a minute. Tell it exactly what you want changed, because vague requests produce vague spreadsheets.
It sorts, filters, builds pivot tables, applies conditional formatting and adds dropdown validation natively, meaning the result is a normal Excel feature you could have clicked yourself, not something fragile that only Claude understands.
Rick's tip
It warns you before it overwrites existing data, and every edit is highlighted so you can review it. If it does something you do not like, undo works exactly as it always has. Keep a copy of the original for the first few sessions anyway.
Let it build and fix things
This is where it stops being a helper and starts being the person who used to do this for you. Errors first: it finds the root cause of a #REF! or a #DIV/0, not just the cell showing it. Then building from scratch, with formulas that stay live.
It works across tabs and across whole models, it can change an assumption while keeping every downstream formula intact, and you can drag a PDF or another file into the side panel as context. If you want to see how far that goes, Claude's finance agents build full stock valuations in Excel this way. One thing that catches people out: it can only work on files that are currently open in Excel. It cannot open, create or switch files by itself, so open what you need first.
Move to PowerPoint
The PowerPoint add-in is the same panel and the same install, and the thing it does well is build inside your own template. Open a deck that already has your template applied, then ask.
To turn a report into a deck, either open the report in Word alongside PowerPoint with the "work across files" switch on and say "summarise this Word document into slides," or drop the PDF into the side panel. And it does pinpoint edits without regenerating anything: "simplify the text on slide 3," "combine slides 5 and 6," "reorder to lead with the recommendation."
If you are on the free plan, or on a phone, the normal Claude chat can still make a downloadable .xlsx or .pptx file from a description, and it can edit a file you upload. It is not the same as working inside the open document, but it gets you a first draft. For decks that need real design rather than your template, Claude Design builds and exports them as PowerPoint files too.
The Honest Part
It does not do macros or VBA, it does not do Excel's What-If data tables, and it cannot touch a file that is not open. The workbook or slide content you ask it about is sent to Anthropic's servers to be processed, like anything you paste into Claude, so a spreadsheet full of client data deserves the same care as any other upload, and if you are on Pro, check the model-improvement setting in your privacy settings if you would rather it not be used for training. Usage counts against your normal Claude limits, and a long modelling session eats them faster than chat. And Anthropic's own advice is the right one: review before you send anything to a client, because it is fast and good, not infallible.
ChatGPT has its own Excel and PowerPoint add-ins now too, and the Excel one is on every plan including Free, so if you live in ChatGPT it is worth a look. I use Claude's because the cell citations and the template-aware decks are the two things I actually needed.
Install it tonight, open the ugliest spreadsheet you own, and ask Step 2's first prompt. Watching it click through to the cells is the moment this stops feeling like a chatbot.