When a plain formula or pivot table is better than AI

Which jobs need exact answers?

Any job where a wrong figure costs money or trust. Think invoices, GST or sales tax totals, pay, stock counts, loan repayments and anything you'll hand to an accountant or the tax office.

Two questions sort most jobs. Would a wrong answer cost money? Must the answer be the same every time you open the sheet? If it's yes to either, use a formula or PivotTable.

Why does a plain formula suit those jobs?

A formula follows fixed rules. Give it the same cells and it gives the same answer, and you can see exactly how. In Excel, the Evaluate Formula tool shows the different parts of a nested formula evaluated in the order the formula is calculated.¹

An AI answer is a different kind of thing, and Google's help page warns it may be inaccurate.² Microsoft's page asks readers to verify Copilot's output too.³ That's fine for a draft. It's a poor fit for a figure that has to be right.

What about totals by group?

That's a job for a PivotTable. It adds up a column for each group, such as sales by region or hours by staff member.

By default, fields placed in the Values area are displayed as a SUM.⁴ And it updates when you tell it to: if you add new data to the source, the PivotTable needs to be refreshed.⁴

Microsoft says to organise the data in columns with a single header row.⁴ Do that and the same PivotTable keeps working month after month.

Where does AI still help?

As a helper that sets up the exact tool. Microsoft says Copilot can create new columns or rows that calculate values from your existing data, and explain how each formula works.³ The result is a normal formula you can read, test and keep.

The safer pattern: let AI draft the formula or PivotTable. Check it with the testing steps. After that, let the formula do the calculating.

What are the limits of AI functions inside cells?

They suit text jobs better than arithmetic. Google's AI function returns text only, and it fills just the first 350 selected cells in one go.²

For a column that has to be filled the same way every month, that's a poor base to build on.

Quick guide

AI can still suggest what to look at. Just don't let it be the last step before a number goes out the door. For how the AI tools work, see the overview of spreadsheet AI.