ChatGPT for Excel: Two Ways to Skip the Formula Guesswork

Every few weeks somebody in one of my Excel classes asks the same question in a slightly different way: “What’s the formula that adds up the sales, but only for one region, and only for this year?” They know exactly what they want. They just can’t remember whether it’s SUMIF or SUMIFS, or which argument goes where. So they build it by hand with a filter and a subtotal, and then they do it all again next month. That is the exact moment ChatGPT for Excel earns its keep.

Knowing the result you want but not the syntax that produces it is precisely the gap it fills. It is very good at turning a plain-English description of an outcome into a working formula, and it is even better at telling you why the formula you already wrote is broken. What it is not good at is guessing what your spreadsheet looks like, and that is where most people’s first attempt falls apart.

Here are the two I show people first. Both take about ten minutes on a file you already have open.

Use ChatGPT for Excel Formulas You Can Describe but Can’t Remember

The trick is to stop asking for “a formula to total sales by region” and start handing over the three things ChatGPT cannot see: your column letters, your row range, and your Excel version. Open a chat and type something shaped like this:

Column A is Invoice Date, B is Customer, C is Region, D is Amount. My data runs from row 2 to row 1840. I'm on Microsoft 365. Write one Excel formula for cell H2 that totals column D where column C is "Northeast" and the date in column A falls in 2026. Give me the formula first, then explain each argument in one line.

What comes back is a complete SUMIFS with the date criteria already built correctly — the part people get wrong — along the lines of =SUMIFS($D$2:$D$1840,$C$2:$C$1840,"Northeast",$A$2:$A$1840,">="&DATE(2026,1,1),$A$2:$A$1840,"<="&DATE(2026,12,31)). You paste it into H2 and you’re done. Building that by hand means remembering that a date comparison has to be assembled as text with an ampersand, which almost nobody gets right the first time.

Asking for the one-line explanation matters more than it sounds. It turns a copied formula into something you can actually change next month when the region is different, and it is how you spot a wrong answer before it lands in somebody’s report.

The gotcha: if your dates are stored as text — left-aligned in the cell, which is common right after an export from an accounting system — that formula quietly returns zero with no error at all. Before you trust the number, drop =ISNUMBER(A2) into a blank cell. If it says FALSE, fix the column before you go any further. And when you paste a sample of your sheet into any AI tool, use a few invented rows rather than real customer records.

Paste the Error and the Actual Cell Contents, Not Just the Formula

The second habit is for the formula you already have — the one showing #VALUE! at nine in the morning. Excel’s little green triangle tells you what broke. It never tells you why. ChatGPT will, but only if you hand over the evidence.

Include three things: the formula exactly as it sits in the cell, the error you’re seeing, and what the referenced cells really contain. Click each one and read the formula bar — don’t go by what the cell looks like on screen. For example:

This formula returns #VALUE!: =A2*B2. A2 displays as 1,240 but the formula bar shows "1,240 " with a trailing space. B2 contains 0.07. Tell me the most likely cause, give me a corrected formula, and give me a one-cell test that proves the cause.

You get the diagnosis — a number stored as text, so Excel can’t multiply it — a repaired formula such as =VALUE(SUBSTITUTE(TRIM(A2),",",""))*B2, and a check like =ISTEXT(A2) to confirm it before you change anything. Ask for that test every time.

The gotcha: if you paste only the formula and the error, ChatGPT will invent a plausible-sounding cause and state it with total confidence. It has no way to see your data. Describing what the cells actually contain is what turns a guess into a diagnosis. And when the fix works, run it down a copy of the column first — a cleanup formula that silently strips the leading zero off a part number is worse than the error you started with.

Plenty more on the calendar

If you want to watch both of these done live, on a real spreadsheet, with the mistakes included, my ChatGPT for Excel session runs on Thursday, October 15. We go through writing formulas from a description, cleaning up a messy export, debugging the errors that come out of it, and building quick summaries — all with prompts you can copy and reuse the same afternoon.

The full current schedule is on the front page of PCWebinars.com, and new dates go up as they are confirmed. Register for this one, or have a look through the others and pick whichever is closest to the work on your desk right now.

About your trainer

I’m Tom Fragale. I’ve been a computer trainer and consultant for more than 30 years, and I’ve taught well over 30,000 people how to get more out of the software they already own — Excel, Access, Power BI, Word, Outlook, and now the AI tools that sit on top of all of it: Claude, ChatGPT, and Microsoft Copilot. My background is applied rather than theoretical. Alongside the teaching I build real databases and reporting systems for clients in Excel, Access, and Power BI, so the examples I bring to class are the problems I ran into last week, not textbook exercises. I also publish free tutorials on YouTube and longer courses online.

Come find the schedule, the recordings, and the free material at PCWebinars.com.