Using AI for Spreadsheet Work, and Always Checking the Formulas

What AI does well with spreadsheets

Working in a spreadsheet, you often know exactly what result you want but not which function gets you there. That is where AI makes a genuinely useful assistant. It can turn a plain description into a formula, such as adding only the rows that meet a condition, joining two tables by name, or pulling the month out of a date, and it can explain why the formula looks the way it does. It is also handy for guessing the cause of an error message or suggesting an order for cleaning up messy data. But the more useful it is, the more it costs when you trust the output blindly, because the numbers in a spreadsheet end up in reports and approvals.

Let the sheet calculate; let the AI write formulas

Conversational AI builds its answers by continuing text, so when it handles a lot of numbers, the arithmetic can quietly go wrong. Paste in a table with dozens of rows and ask for a total or an average, and you may get a plausible but wrong figure, with no sign that anything is off. So there is one rule: do not ask for the resulting number, ask for the formula that produces it. Put the formula in the sheet and the program does the arithmetic exactly, and the result updates when the data changes. Copying numbers from an AI answer into cells by hand is hard to check and impossible to reuse.

What to tell it when you ask

Describing the structure of your table makes a correct formula far more likely. The AI cannot see your screen, so spell out the following.

• Which column holds what, and which row the headers are in
• How far down the data goes, and whether it will grow
• Whether there are blanks, duplicates, or cells mixing text and numbers
• Which program you use and its language setting (function names and separators can differ)
• The result you want, written out as a two- or three-row example

How to check the formula you get

A formula can return a result without an error and still be wrong. No error only means the syntax is valid, not that the value is what you wanted. Check it in this order.

• Try it first on a small example of about five rows that you can work out by hand
• Deliberately add edge cases such as blanks, zeros, negatives and duplicates
• Make sure the range reaches the last row of data and does not include the header
• Copy it down and confirm that cells which should stay fixed do not shift
• Get the same value another way, with a filter or a different function, and compare

Traps that catch people

When an AI-written formula is wrong, the cause is usually the data rather than the formula. Cells that look like numbers but are stored as text drop silently out of totals. Dates behave completely differently depending on whether the program recognises them as dates or just as text. The screen may show two decimal places while the real value is longer, so adding up the displayed numbers does not match the total. The AI may also mix in functions from a different program, or invent a function with a plausible name. When you see a function you do not recognise, check the program's help to confirm it exists and the arguments are in the right order.

When you hand over data clean-up

You can also ask AI how to standardise names, split addresses crammed into one cell, or remove duplicate rows. Always copy the original first and work on the copy. Note the row count and the totals of key columns before and after, so you can tell at once if rows disappeared along the way. Before removing duplicates, decide what counts as a duplicate, because two different people with the same name are not the same as one person entered twice. Putting the cleaned result next to the original and comparing a few rows at a time is still the most reliable check.

Keep real data out

Avoid pasting whole tables of customer lists, staff salaries or sales ledgers. How a service stores and uses what you type varies from one to another, and with work data your company's policy on outside services comes first. You do not need real values to get a formula. Describe the column layout and show a few rows of made-up names and numbers. When you move the formula into your own sheet, you only need to adjust the cell references.

Checks before you use the result

Before an AI-assisted spreadsheet goes into a report or an approval, confirm the following.

• I got formulas, not numbers, and the sheet did the calculating
• I tested the formulas on a small example and on edge cases
• Row counts and totals match before and after clean-up
• No real customer or staff information went in