Uploading an Excel or CSV file to a chatbot and asking a plain question like “which months had the lowest sales?” often works surprisingly well. But for anyone planning to present those numbers in a report, the real challenge is avoiding a calculation error dressed up as a polished analysis. The decisive factor is whether the AI actually executes code to compute results or simply reads the table and responds from pattern recognition. When code runs, you can inspect how the answer was reached; when it doesn’t, you can’t.
- Code execution matters: ChatGPT and Claude run Python in isolated environments, while Gemini in Sheets works inside the spreadsheet and offers an analysis-steps button.
- File limits vary: Gemini accepts up to 10 files per request at 100 MB each, Claude caps files at 30 MB, and ChatGPT supports .xls, .xlsx and .csv without a published per-conversation limit.
- Known failure modes: Scanned tables, complex layouts, oversized files and disconnected charts are documented weak spots across all three platforms.
How the AI actually computes your numbers
OpenAI’s data-analysis guidance explains that ChatGPT writes and runs Python code in a Jupyter notebook environment for certain tasks. Claude operates similarly: its file creation and editing feature provides a sandboxed environment where it executes code, analyzes uploaded data and generates charts or Excel files with working formulas. Gemini inside Google Sheets works directly within the spreadsheet, and its help documentation includes an analysis-steps button to review what it did.
The distinction is critical. A language model summing forty rows by reading numbers can make mistakes just as it can when citing a fact. A program does not fail at addition; if it fails, the error lies in which rows it selected or how it interpreted a column, and that is reviewable.
What each platform can do with your file
All three accept spreadsheets, with different limits according to their help pages. ChatGPT supports .xls, .xlsx and .csv files, plus PDF and text formats. It can display results as interactive tables and create charts, with interactivity for bar, line, pie and scatter plots. OpenAI does not publish a size or per-conversation file limit on that page, noting that it varies by model, plan and configuration.
Gemini offers two paths. In the Gemini app, you can upload up to 10 files per request, subject to availability, at up to 100 MB each, and request charts you can later edit. Inside Google Sheets, Gemini creates tables, formulas, pivot tables and charts, fixes formulas that return errors and answers questions about the data. That second route requires a paid plan: as of October 2026, data analysis in Sheets is available in Google AI Pro and Ultra and in Workspace Business Standard and higher tiers.
Claude creates and reads .xlsx, CSV and TSV files with a maximum of 30 MB per file. The feature is available on all plans, including the free tier; on Free, Pro and Max it is enabled by default and controlled in Settings under Capabilities.
Where they go wrong, according to their own makers
The companies document specific failures. OpenAI warns that ChatGPT may fail to extract exact values from tables in images, scanned files or documents with complex visual layouts. It also notes that ChatGPT may choose an analysis or chart type that does not match your intent on the first attempt.
Google cautions that if you exceed the model’s reading capacity, responses may not account for all content and may lose details scattered across the file. In Sheets, a chart inserted by Gemini goes to a new tab with its own data and does not update when the originals change. ChatGPT’s Python environment cannot make web requests or call external services, while Claude’s network access depends on configuration.
Google closes its page with a general warning that applies to all three: do not use these features as financial or professional advice, because they may provide inaccurate information.
How to verify results before relying on them
You do not need to know how to program to check the essentials. Ask to see the code or steps: in ChatGPT and Claude, ask what was calculated and with which columns; in Sheets, open the analysis steps. Check assumptions, such as whether blanks were treated as zeros or whether “1,500” was read as one thousand five hundred or as one point five. Do a manual calculation with the spreadsheet’s own functions and compare. Review returned formulas by clicking a few cells and reading the ranges they use. Prepare the file properly with clear headers, one row per record and no empty rows or columns.
When the AI provides a figure that does not come from your file, such as an industry average or a report statistic, apply the same skepticism you would to any citation and verify that the source actually exists.
Can you upload your company’s spreadsheet?
It depends on the plan and settings, and on personal versions the prudent approach is to avoid client or employee data. On ChatGPT Free, Plus and Pro, using conversations for training is enabled by default unless you turn it off; on Business, Enterprise and Edu plans it is not used by default. On Claude, consumer plans only use chats for training if you give permission. In Gemini in Sheets, conversations are not saved to your Gemini Activity.
Two more details matter. Google warns that if a sheet has users outside your organization, anything Gemini adds may be visible to them. Anthropic explains that with network access enabled, a prompt-injection attack could in theory lead Claude to send data outside, which is why it recommends that businesses start with the network disabled.
Spreadsheets are probably where these tools perform best and where it is easiest to fool yourself. A clean chart and a confident sentence like “sales fell 12% in March” look authoritative. The sensible approach is to treat them like a very fast intern: let them do the heavy lifting, ask them to show their work and do not sign off on anything you have not checked with your own sum.