A fluent explanation can make a spreadsheet formula feel settled before it has calculated one real edge case. Microsoft explicitly says AI-generated formulas can be inaccurate and should be reviewed and verified. A five-row test often reveals more than another paragraph of explanation.
Write down the rule in plain language
Suppose a household table should calculate quantity × unit price, but leave the result blank when quantity is missing. State that rule before asking for a formula. Decide whether zero is a real value, what a blank means and which currency or measurement unit is used.
Create a small test table with answers you can calculate mentally:
- a normal row, such as 2 × 5;
- a quantity of zero;
- a blank quantity;
- a decimal value;
- the last row of the intended range.
Add a date example if the formula handles dates. Use invented data rather than copying sensitive figures into a new tool.
Compare values, not only appearance
Enter the formula in the test column and calculate the expected answer separately. A displayed zero may hide the difference between “nothing entered” and a real zero. A date can be stored as text while looking plausible. Check the cell’s underlying value and format.
Copy the formula down and inspect how references move. A range ending one row early may pass the first four examples and fail precisely at the boundary.
Test in a copy before applying broadly
Keep the original workbook unchanged or use version history. If an AI feature offers edit, plan and chat modes, choose a mode that matches the risk: a proposal in chat is easier to inspect than an immediate workbook-wide edit.
After the five rows pass, try one additional awkward case from the real sheet. The goal is not to prove the formula correct for every possible input; it is to catch obvious assumptions before they spread through hundreds of rows.