A bad formula explanation reads like “this VLOOKUP looks up Sheet2!A:B.” A good one names the business rule the formula enforces, the edge cases it silently handles, and exactly what would break it — enough that a colleague can change the formula without breaking the workbook. These prompts get you the second kind.
TL;DR
- Paste the formula plus 3-5 sample rows into Copilot in Excel or the “Ask Gemini” side panel in Google Sheets, then use one of the 12 prompts below.
- The single most useful one is prompt #1 (plain-English breakdown). Prompts #3, #4, and #6 are the refactor workhorses.
- As of June 2026, Excel’s in-cell
=COPILOT()function is still rolling out (Beta/Frontier, GA expected around December 2026) and needs a paid Copilot license. Pasting into Copilot Chat or the Gemini side panel works on far more accounts. - Always feed the AI real sample data. With formulas alone it guesses what the columns mean; with rows attached, the explanation is concrete.
Who this is for
Analysts inheriting someone else’s spreadsheet, finance and ops teams who maintain the same recurring sheet every close, and anyone who has stared at a 120-character LAMBDA wondering where to even start.
Where to run these prompts (June 2026)
You do not need the newest in-cell AI to get good explanations. The three practical options:
| Surface | How to access | Notes (as of June 2026) |
|---|---|---|
| Copilot Chat in Excel | Paste formula + a few rows into the Copilot pane | The old “highlight column → Explain Formula” flow was removed for free users; the paste-into-chat workaround still works |
=COPILOT() in-cell function | Type =COPILOT(prompt, range) in a cell | Beta / Frontier / Insider only, requires a Business or Enterprise Copilot license; GA targeted ~Dec 2026 |
| ”Ask Gemini” side panel in Google Sheets | Click “Ask Gemini” (top right) | Explains formulas and walks you through error fixes; hover over an errored cell and Gemini will analyze it |
If you have neither subscription, paste the formula into ChatGPT (GPT-5.5), Claude (Sonnet 4.6), or Gemini 3.1 Pro in a browser. They explain Excel and Sheets syntax well; they just can’t see your live grid, so attach the sample rows yourself.
A quick compatibility note before you translate
XLOOKUP, LAMBDA, and LET all exist in both Excel and Google Sheets (Sheets added them in 2022), so prompts #4 and #6 work in either tool. The one trap: Excel’s named LAMBDA functions and Google Sheets’ Named Functions are not cross-compatible, so prompt #5 (translation) should flag those rather than copy them blindly.
12 copy-ready prompt templates
Each prompt expects you to paste the actual formula where it says [formula]. Wrapping the formula in backticks keeps the AI from mangling it.
1. Plain-English formula explanation
Explain this Excel formula: [formula]. Output: (1) one-sentence purpose, (2) step-by-step what each part does in plain English, (3) inputs / outputs / edge cases, (4) what would break it.Swap in: the formula. Attach 3-5 sample rows so the explanation references real columns, not guesses.
2. Business-logic explanation
For this formula used in [context], explain the business logic it implements, not just the syntax. Output: one paragraph on the business intent + one paragraph on the mechanism.Swap in: formula, context (e.g. “monthly revenue close, deduping refunds”).
3. Simplification candidate
This nested formula is hard to read: [formula]. Propose two simplifications: (a) using helper cells, (b) using newer functions (LET / LAMBDA / IFS). For each, state the trade-off (readability vs. keeping it in a single cell).Swap in: the formula. LET is the safest first step — it names sub-expressions without changing behaviour.
4. VLOOKUP → XLOOKUP / INDEX-MATCH
Replace this VLOOKUP [formula] with XLOOKUP and INDEX-MATCH alternatives. Show all three side by side. Note which is best for: (1) future maintenance, (2) error handling, (3) speed on large sheets.Swap in: the formula. XLOOKUP handles left-lookups and exact-match-by-default, which removes the two most common VLOOKUP bugs.
5. Excel ↔ Google Sheets translation
Translate this formula from [fromTool] to [toTool]: [formula]. Flag any functions that do not exist or behave differently (ARRAYFORMULA, named LAMBDA functions, regex behaviour). Output the translated formula + caveats.Swap in: formula, fromTool, toTool. Excel named LAMBDAs and Sheets Named Functions do not port — expect this prompt to call that out.
6. LAMBDA decomposition
Decompose this LAMBDA: [formula] into named helper LAMBDAs (or LET steps). Output a refactored version with each piece named and a one-line comment per step. Favour readability over brevity.Swap in: the formula.
7. Error-handling pass
Add error handling to this formula [formula]: wrap with IFERROR / IFNA where it genuinely helps. Do not blanket-suppress errors — keep #VALUE! and #REF! visible so real bugs still surface.Swap in: the formula.
8. Volatile-function audit
Audit these formulas for volatile functions (NOW, TODAY, RAND, INDIRECT, OFFSET) that force the whole workbook to recalculate. For each: a non-volatile alternative + when it is fine to keep the volatile version.9. Named-range / structured-reference conversion
This formula uses raw ranges like Sheet1!A2:A1000: [formula]. Convert it to named ranges or structured Table references (Table1[Column]). Show the rewrite + how to define the names.Swap in: the formula.
10. Sheet documentation block
Generate a documentation block for this sheet: (1) Purpose, (2) Inputs (where the data comes from), (3) Outputs (what people downstream use), (4) Key formulas with a one-line explanation + their cells, (5) Owner + last-updated date.11. Power Query / Pivot trade-off
This formula [formula] could instead be a Power Query step or a Pivot Table. Decide between: (1) keep it as a formula because…, (2) move to Power Query because…, (3) use a Pivot because… Pick one with a 3-line rationale.Swap in: the formula.
12. Whole-sheet formula audit
Audit this sheet for: (1) hardcoded numbers that should be inputs, (2) formulas with more than 5 levels of nesting, (3) inconsistent formulas across rows (some cells edited, some not), (4) circular references. Output a prioritized fix list.How to get sharper answers
- Attach sample rows, not just the formula. AI invents what
[ColD]means unless it can see the data. This is the single biggest quality lever. - Name the failure you saw. “This returns #N/A for ~30 of 500 rows” gets a targeted answer; “explain this” gets a textbook.
- Ask for the change, then the diff. “Rewrite with XLOOKUP and tell me what behaviour changes” catches the silent gotchas (sort order, approximate match) that bite later.
- Verify on a copy. Paste the AI’s rewrite into a duplicate column and compare against the original output before you delete anything.
- Don’t let it invent numbers. AI will happily fabricate plausible values if you ask it to “fill in” data. Keep it on explaining and refactoring, not generating facts.
Common mistakes
- Pasting the formula with no sample data, then getting a generic, hand-wavy explanation.
- Accepting a VLOOKUP→XLOOKUP rewrite without checking that approximate-match behaviour didn’t change.
- Wrapping everything in IFERROR, which hides the #REF! that was telling you a column got deleted.
- Refactoring a formula that is actually wrong. Fix the bug first, then document — a clean explanation of broken logic is worse than no explanation.
- Trusting a cross-tool translation of named LAMBDA functions, which do not port between Excel and Sheets.
FAQ
- Does Excel have a built-in “explain this formula” button? Copilot in Excel can explain formulas, but the old free “highlight column → Explain” flow was removed. The reliable path is to paste the formula plus a few rows into Copilot Chat and ask. The in-cell
=COPILOT()function exists too, but as of June 2026 it’s Beta/Frontier and needs a paid Copilot license (GA targeted ~Dec 2026). - Can Google Sheets explain a formula? Yes. The “Ask Gemini” side panel explains formulas and walks you through fixing errors. Hover over a cell showing an error and Gemini can analyze what went wrong.
- Do these prompts work without a paid subscription? Yes. Paste the formula and sample rows into a free chat (ChatGPT with GPT-5.5, Claude Sonnet 4.6, or Gemini 3.1 Pro) in your browser. You lose live access to the grid, so attach the rows yourself.
- Will the AI’s rewrite be safe to ship? Treat it as a first draft. Compare the rewrite’s output against the original in a duplicate column before deleting anything — especially for VLOOKUP→XLOOKUP swaps, where match behaviour can change silently.
- Can AI generate the spreadsheet data for me? No. AI invents plausible-looking numbers. Keep it on explaining and refactoring; connect formulas to real data sources yourself.
- Should I document the formula in the sheet itself? Yes — prompt #10 produces a documentation block you can paste into a hidden tab or a “README” sheet so the next person inherits the logic, not just the cells.
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Tags: #Prompt #Productivity #Excel #Formula