Tool
Claude for Excel (Microsoft 365 add-in)
Price
Included in Pro, Max, Team and Enterprise
Time
10 min
Level
Beginner

Many business owners live with an inherited workbook: a forecast built by an accountant, an invoice tracker patched together over the years. Nobody dares touch the formulas any more, and a #REF! error can sit there for months. The Claude for Excel add-in is made for exactly this: you ask a question in a pane on the right, Claude reads the tabs and answers with the cells involved, which you click to check.

Before installing: is your Excel compatible

  • Supported: Excel on the web, Excel on Windows with a Microsoft 365 subscription (build 16.0.13127.20296 or later), Excel on Mac from version 16.46.
  • Not supported: Excel 2016 and 2019 perpetual licences, Excel on iPad and on Android.
  • You also need a paid Claude plan: the add-in counts against the same usage limits as your claude.ai conversations.

Install the add-in

  1. Open the official listingGo to the Claude for Microsoft 365 listing on Microsoft's store (AppSource), the one Anthropic's help pages link to.
  2. Install itClick “Get it now” and follow the steps with your Microsoft account.
  3. Activate it in ExcelOpen Excel, then the add-ins menu (Home, Add-ins on Windows; Tools, Add-ins on Mac) and choose Claude.
  4. Sign inSign in with your Claude account. The pane opens to the right of the workbook.

The setting to change right away

In the pane's settings, the Instructions field applies to every conversation in Excel. This is where you set your language and number formats once, instead of repeating them in every request:

Instructions
Always answer in English, in short sentences.
Amounts in dollars with thousand separators. Dates as MM/DD/YYYY.
Before changing a cell, tell me which cells you will change.
Never delete a sheet or a column without my approval.

5 useful prompts for a business owner

  1. Understand a figureThe starting point when you take over a workbook you did not build.
    Prompt
    Walk me through how the total in cell F42 of the Summary sheet is
calculated, step by step, citing every cell used. Also tell me which
assumptions move this result the most.
  2. Test an assumption without breaking formulasClaude changes the value and lets dependent cells recalculate.
    Prompt
    In the Assumptions sheet, change the average basket from $45 to $49.
Show me the impact on December's margin and cash position.
Do not change any formula.
  3. Find the source of an errorClaude traces back to the cause, not just to the cell showing the error.
    Prompt
    Cell H15 in the Cash sheet shows #DIV/0!. Find the cause and suggest
a fix, but do not apply it until I approve.
  4. Tidy up a trackerThe add-in can sort, filter, apply conditional formatting and create dropdown lists.
    Prompt
    In the Invoices sheet: sort by due date, colour in red the unpaid
invoices more than 30 days overdue, and add a dropdown list
"Paid / Pending / Reminded" in the Status column.
  5. Build a simple forecastClaude can create a model from a description, or fill in an existing template.
    Prompt
    Create a "Forecast 2027" sheet over 12 months: revenue, fixed costs,
variable costs at 35% of revenue, profit and cumulative cash.
Put the assumptions in editable cells at the top of the sheet,
and explain each formula in one line.

Limits to know

  • Macros, VBA and data tables are not supported.
  • Anthropic advises against using it for client deliverables without review, or for critical calculations without verification.
  • Claude warns before overwriting existing data, and asks for confirmation before a risky operation.
  • Chat history stays in your browser. On the server side, data is deleted within 30 days, except in cases set out in Anthropic's policy.

Be careful. Only use the add-in on workbooks you trust. A downloaded template or a file sent by a supplier can contain hidden instructions aimed at the AI, pushing it to extract or change data. Work on a copy before a big change, read every confirmation request, and think twice before giving AI a workbook with sensitive client or staff data.

Sources

Your figures live in several files and you retype the same numbers every month? I can connect those files and automate the report: see my automation offer.