Excel Copilot "Explain This Formula" in 2026: Understand Any Formula Instantly with AI
Published: June 11, 2026 | Category: Excel | Reading Time: 6 min
Excel formulas have always had a reputation for being cryptic. A nested IF inside a VLOOKUP wrapped in an IFERROR, or a LAMBDA function referencing a dynamic array — these can look like ancient runes to anyone who did not write them. In 2026, Microsoft Copilot in Excel includes a powerful set of formula intelligence features that change this entirely. The "Explain this formula" capability lets you select any formula in any cell and get an instant, plain-language explanation of exactly what it does, why it is structured that way, and how to modify it. This guide covers every aspect of this feature and how to get the most from it.
Why Formula Explanation Matters
Spreadsheets are handed down between colleagues, inherited from predecessors, or built under time pressure with minimal documentation. The result is workbooks full of formulas that nobody fully understands — including the people using them. Incorrect assumptions about what a formula does lead to reporting errors, bad decisions, and hours of debugging. The ability to instantly explain any formula eliminates this problem.
Beyond error prevention, formula explanation accelerates learning. Rather than reading through help documentation or watching tutorials, you can reverse-engineer real formulas from real workbooks and understand them in context. This is one of the fastest ways to level up your Excel skills in 2026.
How to Use Explain This Formula
Method 1: Via the Copilot Pane
Click any cell that contains a formula.
Open the Copilot pane by clicking the Copilot button on the Home ribbon, or press Alt + Shift + C.
Type: "Explain the formula in [cell reference]" — for example, "Explain the formula in D5."
Copilot returns a structured explanation covering what the formula calculates, how each component works, and what the result represents.
Method 2: Right-Click Context Menu
Right-click any formula cell and select Explain with Copilot. This opens the Copilot pane pre-populated with an explanation request for that specific cell. This is the fastest method when you are exploring an unfamiliar workbook.
Method 3: Hover Tooltip (New in 2026)
In 2026, Excel added a lightweight hover explanation: hold Alt and hover over a formula cell to see a one-sentence plain-language summary in a tooltip, without opening the full Copilot pane. This is ideal for quick validation while navigating a workbook.
What a Copilot Formula Explanation Looks Like
Here is an example. Suppose cell D5 contains this formula:
=IFERROR(XLOOKUP(C5,SalesData[CustomerID],SalesData[Revenue],"Not found",0),"Error in lookup")
Copilot might explain it like this: "This formula looks up the value in cell C5 (a Customer ID) in the CustomerID column of the SalesData table. If it finds a match, it returns the corresponding Revenue value. If there is no match, it displays Not found. The outer IFERROR function catches any unexpected errors in the lookup process and displays Error in lookup instead of an error code. The 0 as the fifth argument means the lookup searches for an exact match only."
Notice that Copilot does not just parse the syntax — it explains the business logic and the intent behind each component. This is far more useful than the Excel help documentation, which describes function arguments in abstract terms.
Going Further: Modify and Fix with Copilot
Once you understand a formula, you can ask Copilot to modify it without rewriting it from scratch:
"What would I change to make this return a default of 0 instead of Not found?"
"How would I adapt this formula to look up by email address instead of Customer ID?"
"This formula is returning the wrong values — what might be wrong?"
Copilot will analyse the formula structure and suggest specific changes, explain why those changes work, and offer to insert the updated formula directly into the cell. This dramatically shortens the debugging and iteration cycle.
Formula Explanation for Complex 2026 Functions
Some of the most powerful Excel functions added in recent years are also the most difficult to read. Copilot excels at explaining:
LAMBDA functions: Custom functions with their own parameter names can be opaque. Copilot explains what parameters the LAMBDA expects and what calculation it performs.
BYROW, BYCOL, MAKEARRAY: Array-manipulation functions that apply operations row-by-row or column-by-column. Copilot explains the iteration logic in plain terms.
GROUPBY and PIVOTBY: Dynamic aggregation functions. Copilot identifies the grouping key, the value being aggregated, and the aggregation method.
REGEX functions: Pattern-matching formulas. Copilot translates the regex pattern into a plain description of what text it matches or extracts.
Python in Excel formulas: For cells containing =PY() with embedded Python code, Copilot explains what the Python script computes.
Tips for Getting the Best Explanations
Be specific about what confuses you: rather than just asking for an explanation, ask what the third argument of the XLOOKUP does, or why there are two nested IFs.
Ask for examples: request that Copilot show you sample inputs and expected outputs to verify your understanding.
Use follow-up questions: each Copilot explanation is conversational — you can ask for clarification, request simplification, or ask what would happen if a specific argument changed.
Conclusion
The ability to explain any formula instantly is a fundamental shift in how Excel users interact with spreadsheets. It removes the fear from inherited workbooks, accelerates skill development, and reduces formula errors across teams. You no longer need to be an Excel expert to understand what a spreadsheet is doing — you just need to ask Copilot.
Action step: Open the most complex workbook in your organisation, find the formula that has always confused you, and ask Copilot to explain it. Then share what you learned with your team. Understanding shared spreadsheets is a team responsibility — and in 2026, there is no reason for anyone to work with formulas they do not understand.
