Excel AI: What to Leave to Copilot, ChatGPT and Claude

Excel AI is the umbrella term for tools that read a workbook, write formulas, tidy messy data, label text columns and explain results in plain language. Today they reach Excel in three ways: Microsoft Copilot built into Excel, the ChatGPT and Claude add-ins installed into Excel, or a file uploaded to a chat tool and analyzed with Python code. In Google Sheets, the equivalent is the AI function. They all share one limit: a language model does not compute a number the way a calculator does; it predicts the number, the way it predicts the next word in a sentence. When it hands the calculation to a formula or to code, the result is as reliable as that formula. When it types the number into the chat itself, it is not.

This article splits Excel work into two groups: the jobs to hand to AI and the ones that have to stay in a formula. The dividing line fits in one sentence: if you cannot see the formula or code that produced a number, that number does not go into the report.

Excel AI tools: Copilot, ChatGPT, Claude and Google Sheets

What sets them apart is where they run and what produces the result:

• Microsoft Copilot: Works inside Excel, in a pane on the right. It reads your tables, suggests formulas and inserts them into cells, and builds PivotTables and charts. With Edit with Copilot, the capability Microsoft first introduced as Agent Mode and has since folded into the standard Copilot experience, it plans a multi-step task, applies it in the workbook and checks the result; the general term for this way of working is an AI agent. Copilot requires a Microsoft 365 subscription, and which features you get depends on your plan.
• Claude: Anthropic's AI assistant, which works inside Excel through the Claude for Excel add-in. According to Anthropic's documentation, the add-in is generally available on the Pro, Max, Team and Enterprise plans. It answers questions about the workbook with cell-level citations that take you to the referenced cell when clicked, and it keeps formula relationships intact when you change assumptions.
• ChatGPT: OpenAI's ChatGPT for Excel add-in runs in a sidebar next to your workbook. According to OpenAI's help center, it has been available on all plans, free ones included, since May 2026, with limited usage on Free and Go. Without the add-in, you can still upload an Excel or CSV file to a chat; for many analyses, ChatGPT writes and runs Python code and returns the result as tables and charts. When it uses Python, you can open the code it ran and read it.
• Google Sheets: The AI function is typed into a cell and uses your prompt to generate, summarize or categorize text. According to Google's help page, its responses are limited to text and it has no access to your entire spreadsheet; to give it data or context, you pass the relevant cells as a range.

Excel's COPILOT function was retired on 14 September 2026

Microsoft removed the =COPILOT() function from Excel on 14 September 2026. According to Microsoft's support page, it was a preview feature, available only through the Frontier and Microsoft 365 Insider programs. Results calculated earlier stay in the workbook as cached values; when a cell recalculates, Excel no longer recognizes the function and returns a #NAME? error. For the same jobs (summarizing text, classifying data, generating content), Microsoft points users to the Copilot pane, where you describe the task in your own words.

When Microsoft first released the function to Beta Channel users in August 2025, it already advised that the output should be reviewed and validated for accuracy, especially for critical business decisions and reports (The Register). An AI result in a cell looks like a formula but does not behave like one: a formula returns the same result for the same input every time, while a language model may answer the same question differently each time; we cover the accuracy limits of generative AI in business in a separate article. Türkiye's Personal Data Protection Authority (KVKK) lists hallucinations and inconsistent outputs among the risks inherent in generative AI models in its guide to generative AI and personal data protection (November 2025, in Turkish).

If you have a workbook that contains =COPILOT, open Find and Replace, set Within to Workbook and Look in to Formulas, and search for it. Rebuild the cells that produce numbers with functions such as SUM, AVERAGE, IF and XLOOKUP; copy text results and paste them as values before the cell recalculates, or request them again from the Copilot pane.

What AI does well in Excel

The jobs where AI is strong in Excel have one thing in common: the output is a visible formula, a piece of code, or a text judgment you can check row by row.

• Writing formulas: Turns a request such as "March total for dealers in the West region" into a SUMIFS formula. Once the formula is in the cell, Excel does the math, and the formula bar shows exactly what is being calculated.
• Explaining formulas: Walks you step by step through a nested IF and VLOOKUP formula you inherited, and traces an error back to its source.
• Cleaning data: Standardizes different spellings of the same company name, splits an address held in a single cell into street, city and postal code, and converts dates stored as text into real dates.
• Classifying text: Tags customer reviews by topic and sentiment, and sorts free-text expense descriptions into categories. A wrong label affects only its own row; before accepting the result, check a random sample by hand.
• Turning a recurring transformation into code: Instead of repeating the same clean-up by hand every month, have the AI write it once as Power Query steps or Python code; from then on, the same code produces the same result every month. Read the code before you run it; we cover where AI-written code breaks in a separate article.
• Interpreting the result: Describes what a calculated PivotTable shows and points out notable deviations. The numbers behind that commentary come from formulas.

Leave the math to formulas, not to AI

Grand totals, averages, account reconciliations, VAT, exchange-rate differences and payment-term calculations each have exactly one correct answer. In these jobs, the AI's role is not to do the calculation but to write the formula or code that does it. Anthropic itself, in its documentation for Claude for Excel, does not recommend the add-in for audit-critical calculations without verification.

Ask three questions of every number an AI tool gives you:

1. Which formula or code produced this number, and can I see it?
2. If I ask the same question again, will I get the same number?
3. Can I compare it with a control value calculated separately in Excel, such as the row count or the grand total?

We built NestAsist, our AI-powered reporting and analytics assistant, on the same rule: it understands the question and builds the right query on your data, and its synthesis engine interprets the result. You can open the query behind every answer, so the question of where a number came from always has an answer.

Why AI-written formulas fail in localized Excel

Chat tools usually write Excel formulas with English function names and commas between the arguments: =SUMIFS(D:D,A:A,"West"). That works in English Excel. Many localized versions of Excel, however, use translated function names, and on Windows, Excel expects arguments to be separated by the list separator set in the regional settings; Microsoft's troubleshooting documentation notes that the comma is the default list separator for the US English locale. In locales that write decimals with a comma, Turkish among them, the list separator is typically the semicolon. The two settings are independent: English Excel on a computer with Turkish regional settings keeps English function names but still expects semicolons. TecnoNest is based in Türkiye, so Turkish Excel is our everyday example: there, the same formula is =ÇOKETOPLA(D:D;A:A;"West").

Type a comma where Excel expects a semicolon and Excel rejects the formula outright with the message "We found a problem with this formula". Fix the separators but keep an English function name in localized Excel, and the cell returns a #NAME? error (shown as #AD? in Turkish Excel).

Even Microsoft's Turkish help pages often write their examples with commas: the Turkish page for XLOOKUP gives the syntax as =ÇAPRAZARA(arama_değeri, arama_dizisi, döndürülen_dizi, ...). On a computer with Turkish regional settings, the same function is typed as, for example, =ÇAPRAZARA(B2;B5:B14;C5:C14).

The fix belongs in the request: tell the tool your Excel language and list separator, for example: "I use Turkish Excel; write the function names in Turkish and separate the arguments with semicolons." Copilot and the ChatGPT and Claude add-ins work inside Excel and write the formula straight into the cell, so this translation problem comes up less often with them; it mostly appears in formulas copied from a chat window. Still, check the formula in the formula bar.

Before you hand an Excel file to AI: personal data, shadow AI and hidden instructions

Excel files often carry personal data: customer names, phone numbers, national ID numbers, salaries, account balances. KVKK addressed this in February 2026 in a document titled Use of Generative AI Tools in the Workplace (in Turkish). The document defines shadow AI as employees using generative AI tools in their work without the organization's knowledge or approval, or outside its institutional control. It notes that meeting notes, internal correspondence, report drafts and information about employees or customers can end up in third-party AI tools this way, and it stresses the importance of a clear organizational usage policy. For organizations in Türkiye, the Authority's November 2025 guide also covers transfers of personal data abroad through generative AI systems under Article 9 of Law No. 6698. Wherever you operate, the same questions come before any upload: which data goes to which tool, under which account, and where it is processed.

In practice, these four steps reduce the risk the most:

• Remove the personal-data columns you do not need: Analysis usually works without names, phone numbers and ID numbers. Replacing names with customer codes keeps identities out of the file you upload, but it does not make the data anonymous: as long as the code table stays in the company, the data is still personal data. The KVKK document likewise recommends anonymized, generalized and abstract wording when interacting with AI tools.
• Use an account your organization manages: An employee's personal account sits outside the organization's oversight. A written company policy sets out which tool is used, with which account and for which types of data.
• Be careful with files from outside: A workbook from a supplier or from the internet can carry instructions hidden in its cells. Anthropic's documentation for Claude for Excel warns that such hidden instructions (prompt injection) can manipulate the add-in into extracting sensitive information or modifying records, and recommends using it only with trusted spreadsheets.
• Test bulk changes on a copy first: Run wide-ranging AI edits on a copy of the workbook rather than the original, and accept them only after comparing the results.

Where Excel runs out: the question that comes back every week

AI speeds up one-off work in Excel. When the same report is requested every week, and every week the data is exported from the ERP into Excel, cleaned and uploaded to an AI tool, the problem is not in the formula but in the workflow. Three signs show you have reached that point:

• Several versions of the same report circulate by email, and none can be used without first asking which one is current.
• The same clean-up steps are repeated by hand every month.
• Managers wait for a report to answer a simple question such as "Who are our five customers with the highest balances?"

At that point, rather than carrying the file to the AI, take the question to where the data lives. To choose which step of a recurring report flow to automate first, apply the criteria in our guide to process automation: where to start and how to measure it. NestAsist puts these questions directly to ERP and database data; for data security, it can run on-premises on your own servers, so your data never leaves your organization.

Frequently Asked Questions

How do you use AI in Excel?

There are three routes: Copilot inside Excel through a Microsoft 365 subscription, the ChatGPT or Claude add-in for Excel, or uploading the file to a chat tool. Whichever you choose, the most reliable approach is to have the request turned into a formula or code and leave the calculation to that formula. In Google Sheets, the AI function works from inside a cell to generate, summarize and categorize text.

Why does Excel's =COPILOT function return a #NAME? error?

Microsoft removed the COPILOT function from Excel on 14 September 2026. Results calculated earlier stay visible until the cell recalculates; on recalculation, Excel no longer recognizes the function and returns #NAME?. Rebuild numeric results with functions such as SUM, AVERAGE, IF and XLOOKUP; copy text results and paste them as values before the cell recalculates, or request them again from the Copilot pane.

Why doesn't an Excel formula from ChatGPT work in my Excel?

Usually because the formula uses English function names and commas. Many localized versions of Excel expect function names in their own language and arguments separated by the list separator from the regional settings, which is typically the semicolon where the comma is the decimal separator. In Turkish Excel, for instance, SUMIFS is ÇOKETOPLA and XLOOKUP is ÇAPRAZARA. Stating your Excel language and list separator in the request usually fixes it.

Is the total an AI tool gives me in Excel correct?

If a formula or code calculated the total, it is as correct as that formula or code, and you can open it and check. If the AI wrote the number into the chat itself, do not use it without verification; language models can give results that look plausible and are wrong. As a check, calculate the row count and the grand total separately in Excel and compare.

Is it safe to upload an Excel file with personal data to an AI tool?

It depends first on the data. Under Türkiye's Law No. 6698, a file with no personal data, or with data that has been truly anonymized, falls outside the law; if the file does hold personal data, the upload is a processing activity that needs a legal basis under Article 5 or 6, must be limited to what the analysis requires and, if the provider processes the data abroad, must rely on one of the transfer routes in Article 9. Türkiye's data protection authority, KVKK, also describes employees' use of AI tools without the organization's knowledge or approval, or outside its control, as shadow AI and considers a clear usage policy important. Removing the personal-data columns you do not need and using accounts your organization manages reduce the risk the most.

Is there an AI add-in for Excel, and how do you install it?

Yes. The two most common are OpenAI's ChatGPT for Excel and Anthropic's Claude for Excel; both install from Microsoft's add-in marketplace, after which you activate the add-in in Excel and sign in with the matching account. According to Anthropic, Claude for Excel works on the Pro, Max, Team and Enterprise plans, in Excel on the web, in Excel for Windows with a Microsoft 365 subscription and in Excel for Mac. According to OpenAI, ChatGPT for Excel is available on all plans, free ones included, with limited usage on Free and Go. Copilot is not an add-in; it comes built into Excel with a Microsoft 365 subscription.

Can the AI function in Google Sheets replace Copilot in Excel?

The two are built for different jobs. According to Google, the AI function returns only text and has no access to the entire spreadsheet; to give it data or context, you pass the relevant cells as a range. It suits generating, summarizing and categorizing text, while calculations stay with the spreadsheet's own formulas. Copilot works across the tables, formulas, PivotTables and charts in a workbook.