Which tool to choose
To explain an existing formula, the latest free version of any general-purpose AI assistant is fine: the formula is text, and reading text is its job. If instead the formula lives in a huge file with many linked sheets, an assistant that reads the attached spreadsheet understands the references between cells better. For just "what does this line do", simple chat is more than enough.
How to do it
A formula explained in a vacuum is theory. A formula explained on your numbers is understanding: you see the result and understand where it comes from.
- Select the cell, copy the content of the formula bar (not the result, the formula).
- Paste it into the AI and ask for the explanation part by part.
- Add two or three example rows of your data and ask: "what does it return on these values and why".
- If a function inside the formula isn't clear to you, ask for a minimal example of just that one.
- When you want to modify it, describe the change in words and have it rewritten, then test the new version on a scratch cell.
The operational syntax:
Explain this Excel formula to me piece by piece, what each function does:
=IF(VLOOKUP(A2;PriceList!A:C;3;FALSE)>100;"expensive";"ok")
My data: in A2 there's a product code, in the PriceList sheet column C has the prices.
Tell me what it writes in the cell if the price is 150 and if it's 80.
After the explanation, try changing an example value and ask whether the result changes as you expect. It's the fastest way to check that you really understood.
A concrete example
Anna inherits a budget file with a three-line-long formula that nobody knows what it does anymore. She copies it into the AI and writes: "explain this formula to me as if I knew nothing about Excel, and tell me what it calculates on January's data". The AI takes the formula apart: it sums the expenses of a category, but only those after a certain date. Anna realizes that the date hidden in the formula was stuck two years back: that's why the totals were wrong. She fixes it in a minute.
When it does NOT work (and how to fix it)
If the AI explains the formula but your result stays different
The explanation is generic because you didn't give the data. Paste a few real rows and the names of the sheets the formula references: the AI can tell you the problem is an empty cell or a reference pointing to the wrong sheet, not the logic of the formula.
If the formula uses English functions and your Excel is in Italian (or vice versa)
The function names change with the language of the program (IF becomes SE, VLOOKUP becomes CERCA.VERT). Tell the AI: "my Excel is in Italian, give me the function names in Italian". You avoid pasting a formula your program rejects.
If you can't find where to copy the formula
The formula isn't the number you see in the cell: it's in the bar at the top when you select the cell, or by pressing the key that shows the formulas instead of the results. If you can't find it, take a screenshot of the selected cell with the bar visible and ask the AI to read the formula from the image.
A tip from someone who actually uses it
When the AI explains the formula to you, also ask "is there a simpler way to write it?". Often complex formulas inherited from others are complicated out of habit, not necessity. A shorter version is a formula you'll still understand in six months, and one that breaks in fewer places.
Frequently asked questions
Does it work with Google Sheets and other spreadsheets too?
Yes. The logic of formulas is almost identical between Excel, Google Sheets and the others; some function names and the separator change (semicolon or comma). Declare which program you use and the AI adapts the explanation and any corrections.
Can I trust it if the AI tells me the formula is right?
The explanation of what it does, yes. The judgment "it's correct", verify on your numbers: ask what it returns on a case whose result you already know. If it checks out, the formula does what you think.
Isn't it safer to ask a colleague who knows Excel?
An expert colleague gives you the right answer, but only once and when they have time. The AI explains it to you at eleven at night, repeats without getting impatient and lets you ask the stupid question you wouldn't dare ask at the office. The difference isn't competence, it's availability.