Let the sheet do the maths
Explain before you change
Paste a formula (or describe the sheet's columns) and ask what it does in plain English, step by step. This is one of the safest, most useful things AI does. When you inherit a workbook, ask for an explanation of each tab before touching anything. Our Spreadsheet Formula prompt asks the AI to explain the workbook first.
Writing new formulas
Describe what you want in words: "In column F, show the number of days between the order date in B and delivery date in D, or 'pending' if D is empty." Say whether you use Excel or Google Sheets, since functions differ. Test the formula on a few rows where you know the answer before filling it down.
Don't let it do the sums in chat
Chatbots can make arithmetic slips when they calculate in their heads, especially with long lists. Tools that run code or work inside the spreadsheet (Copilot in Excel, Gemini in Sheets, ChatGPT and Claude analysing an uploaded file) are far more reliable, but still check totals against a figure you trust. Never copy a number from a chat reply straight into a report.
Cleaning messy data
AI is good at spotting inconsistent dates, duplicate rows, names spelled three ways and stray spaces, and at suggesting how to fix them. Work on a copy, keep the original, and watch for personal data: a customer list is still a customer list when it is in a CSV. Our guide to messy CSV files covers the tools.
Is there a spreadsheet at work that everyone uses and nobody fully understands? What would you ask about it first?