Decode a long Excel formula with Evaluate Formula and an LLM
Paste the formula into ChatGPT or Claude for a plain-English explanation, then confirm each part with Evaluate Formula and F9 so you aren't relying on a wrong answer.
Tools used
- ChatGPTExplains the formula in plain English
- Excel (Microsoft 365)Evaluate Formula and F9 confirm the actual results
Step navigator
A formula you understand piece by piece, with each piece's result confirmed in Excel.
Anyone staring at a nested formula someone else wrote.
Before you start
On r/excel, a top answer to "best way to audit a complicated formula" was to paste it into ChatGPT. The pushback was about trust: answers that are confidently wrong. The workable version uses AI for the explanation and Excel's own tools to prove it.
Step-by-step instructions
Paste the formula into an LLM and ask for a breakdown
Copy the formula from the formula bar and ask for an explanation of each part. Users in the thread: "Throw it in ChatGPT and ask it to do it", and "when it comes to excel formulas, VBA and small Python scripts - AI shines." Say what the referenced cells contain.
Explain this Excel formula part by part, innermost first. B2 is an order date, C2 is a region code, and Rates!A:B is a lookup table. Formula: <paste>
Treat the explanation as a hypothesis
Another user's caution: "I think the real issue is the hallucinated responses which remove the trust." Check it before you rely on it.
Step through it with Evaluate Formula
Select the cell, then Formulas → Formula Auditing → Evaluate Formula. Select Evaluate to compute the underlined part; use Step In to open a referenced formula and Step Out to go back. Compare each intermediate result with what the AI said.
Why this works
This shows what Excel actually computes, in order.
Check any piece with F9
In the formula bar, select one complete piece of the formula and press F9 to see its value, then press Esc so you don't replace the formula with the value. It's one of the tools r/excel users list for understanding individual formulas.
Test any AI rewrite on a copy
If you ask the AI to simplify the formula, test the new one next to the old one on a copy. One user rates the advice at "like 75% good" and says "you'd definitely want to save a copy and try it before moving on since it sometimes cranks out some non working formulas."
End of guide · Reviewed Oct 26, 2026
Pro tips2
- Ask the AI to rewrite the formula over several indented lines; it is easier to read.
- Ctrl+[ jumps to the cells the formula reads.
Common mistakes2
- Pressing Enter after F9, which saves the value instead of the formula.
- Accepting the explanation without stepping through it.
FAQ2
Does Evaluate Formula work on everything?
ChatGPT or Claude?
Related field guides.
ExcelCombine monthly files with Power Query, using an LLM one step at a time
Point Power Query at a folder of same-shaped files, then use ChatGPT or Copilot only to write or explain individual M steps, testing each one before adding the next.
ExcelTurn a recorded macro into reusable VBA with ChatGPT, then test it on a copy
Record the task, have ChatGPT clean up and comment the code and make the ranges dynamic, then compile, step through and test it on a copy before it touches real data.
ExcelRun a Python analysis in Excel with Copilot's Advanced Analysis
Put the data in a Table in a cloud-saved workbook, start Advanced Analysis in Copilot, let it write Python cells, and read each one before you reuse the code.