Best AI for Excel: which one to use based on what you already pay for

If you’re looking for the best AI for Excel, you may already be paying for it. Microsoft 365 comes with Copilot, Claude and ChatGPT have add-ins that sit inside the spreadsheet, and Google has put Gemini into Sheets.

Most guides are written for American spreadsheets and skip what matters here. In a Spanish Excel the functions have other names and take semicolons, and 03/04/2026 is 3 April. I’ll go through what each one does and what it costs in Spain, and at the end there’s a five-minute test to see whether it gets confused.

Best AI for Excel, based on what you already pay for

Prices in Spain in September 2026:

My advice: start with the one you already have and give it the test further down. If it passes, don’t pay for another. And if you do want to switch subscriptions, which AI to pay for has every plan.

Copilot in Excel: agent mode and which plan includes it

With Microsoft 365 Personal, Family or Premium, Copilot is already in your Excel, behind the button at the bottom right. What Microsoft used to call «Agent Mode» is now edit mode, and it’s on by default: you ask for something and it does it in the sheet, with formulas, charts or pivot tables. If you’d rather go carefully, plan mode shows you the steps before it touches anything.

• It uses AI credits, a monthly allowance that on Family and Premium only the subscription owner gets, not the people you share the subscription with.
• On the home plans, the file has to be in OneDrive with AutoSave on.
• Edit mode has reached the EU in stages. If it only lets you chat, update Excel.
• Microsoft admits it may work less well with data that isn’t in English. Check it with your own sheet.

Premium adds more usage and lets you choose between OpenAI and Anthropic models. At work, Microsoft 365 Business plans include Copilot in Excel at no extra cost, with «standard access» that can slow down at busy times. To check whether you have it, sign in to Microsoft 365 with your work account and look at what it says under your name at the bottom of the home page: «M365 Copilot (Basic)» means yes; with «Copilot Chat (Basic)», you don’t get it inside Excel. The Microsoft 365 Copilot Business licence, which gives you priority, costs €18.20 + VAT per user a month, paid yearly, if you already have a business plan (€15.60 for the first year if you sign up before 31 December 2026). Starting from scratch, Business Standard with Copilot is cheaper: €20.36 + VAT per user a month, paid yearly.

Claude for Excel: understanding and fixing complicated sheets

It’s an add-in from Microsoft’s store, where it’s listed as Claude for Microsoft 365 and also covers Word and PowerPoint. It comes with any paid Claude plan, from Pro, not with the free one. It runs in Excel for Windows with Microsoft 365, on Mac and on the web. Not on the iPad, and not in the one-off purchase versions of Excel 2016 or 2019.

Anthropic built it for serious spreadsheets: you ask where a figure comes from and it explains, citing the cells; you change an assumption without breaking the formulas that depend on it; or you ask it to find the source of a #REF! error. It also sorts, filters and edits pivot tables. No macros or VBA. If you inherit someone else’s workbook and can’t work out how it’s built, this is where I’d start.

ChatGPT for Excel, Google Sheets and Gemini

OpenAI has ChatGPT for Excel and for Google Sheets. Since 5 May 2026 they’ve been available worldwide on every plan: with limited use on Free and Go, and on Plus and Pro drawing on the same allowance as Codex. It’s the only one of the four that works with a free account. It builds sheets from scratch, explains why a formula fails and cleans up formatting and duplicates. On the downside, its conversations don’t use ChatGPT’s memory and macros may not work properly. On a work account, your admin may restrict installation or access.

Gemini is built into Google Sheets with Google AI Pro (€21.99 a month; Google doesn’t list it on the €4.99 Plus plan) or with Workspace from Business Standard up (€13.60 + VAT per user a month, paid yearly). It creates formulas, charts and pivot tables. Google says it works best with its own sheets, so if you have an .xlsx, save it as a Google Sheet first.

What to ask it: five office jobs

The last two are the tricky ones. Files exported from other software sometimes store amounts and dates as text, and then the totals don’t add up. And Anthropic warns that a file from outside can hide instructions meant to trick the add-in, so with a supplier’s spreadsheet, have it ask before changing anything. If you’re comparing quotes, how to compare quotes with AI has a template.

An Excel prompt for Spanish formulas, with no made-up functions

In a Spanish Excel, =SUMIF(A:A,F2,D:D) doesn’t work. There it’s =SUMAR.SI(A:A;F2;D:D), with semicolons because the comma is the decimal separator. If the function doesn’t exist in your Excel you get #¿NOMBRE?, the Spanish #NAME?, and with commas where it expects semicolons it won’t even accept the formula. Microsoft says the separator depends on your computer’s regional settings as well as on Excel, so an English Excel on a laptop set to Spain can want semicolons too.

This bites mostly when you copy formulas from a chat. Dates, on the other hand, are worth watching everywhere: Microsoft’s technical documentation warns that a European-style date written as text can end up stored as text.

Paste this at the start of the conversation:

I use Excel [for Microsoft 365 / 2019] [in Spanish / in English] on a computer set to Spain. When you give me formulas:
- If my Excel is in Spanish, use Spanish function names (SUMAR.SI, BUSCARV, SI.ERROR...). Separate arguments with semicolons.
- Decimal comma and thousands point (1.234,56). Dates are dd/mm/yyyy: 03/04/2026 is 3 April.
- VAT (IVA) at 21, 10 or 4 %, rounded to the cent.
- Only functions that exist in my version (with Excel 2019, no XLOOKUP or BUSCARX). If you're not sure one exists, tell me instead of making it up.
- Explain each formula in one line and tell me which cell it goes in.
- Don't touch the original data: work in new columns or tabs.

In Claude for Excel you can save it in the instructions field in the settings, and in Copilot, under Personalization. In ChatGPT for Excel, paste it every time. In the Canary Islands, Ceuta or Melilla, swap IVA for IGIC or IPSI.

Try it yourself: three invoices with VAT

Before you hand it your real sheet, spend five minutes on this. Open a blank sheet and ask the AI you plan to use:

Build a table with date, client, net amount, VAT rate, VAT and total, and below it the total invoiced per month. Use formulas.
Invoice 1: 03/04/2026, Client A, net 100,00 €, VAT at 21 %.
Invoice 2: 15/04/2026, Client B, net 250,00 €, VAT at 10 %.
Invoice 3: 30/05/2026, Client C, net 1.234,56 €, VAT at 4 %.

Then check:

1. The date. Invoice 1 is from April. If it lands in March, it read the date the American way.
2. The thousands. Invoice 3 comes to €1,283.94 with VAT (1.283,94 € in Spanish format). If you get another figure, it most likely misread the thousands point.
3. The months. April, €396.00. May, €1,283.94.
4. The formulas. The VAT cells must hold formulas, in your Excel’s language and separator, not numbers typed in by hand.
5. The dates. In an empty cell type =ISNUMBER(A2), or =ESNUMERO(A2) in a Spanish Excel, with A2 swapped for a date cell. If you get FALSE (FALSO), it’s text and you won’t be able to group by month.

If it slips up, tell it as you would a colleague («invoice 1 is from 3 April, check how you read dates») and you’ll know what to watch for with your own figures.

What data to keep out of a sheet the AI will read

Give it only what it needs: to get sales by month it doesn’t need to know what each client is called. Before you open the sheet to it:

• Remove, or replace with a code, the names, DNI or NIE numbers, phones and emails of individual clients. Health data, never on a personal account.
• Delete IBANs and card numbers. To reconcile the bank, date, amount and description are enough.
• No passwords or keys, not even on a hidden tab.

Work on a copy with only the columns it needs. With Claude or ChatGPT on a personal account, first check the setting that decides whether they train on your conversations. Microsoft says it doesn’t train on the content of your files on its home plans. For clients’ personal data, check the account, agreement and permissions before uploading it. This also applies to a single query.

For the rest of your office work, see which AI to use for what.

Sources, checked on 26 September 2026: Microsoft 365 prices in Spain and for businesses (in Spanish), Microsoft 365 AI credits, Copilot in Excel FAQ, Claude for Excel, Claude pricing, ChatGPT for Excel and Google Sheets, ChatGPT pricing, Gemini in Google Sheets, and the Spanish prices of Google AI plans and Google Workspace. ChatGPT access and permissions and eligible Gemini editions rechecked on 1 October 2026; other prices and capabilities retain the earlier check date.