Section 01

The hardest part of a formula is rarely typing it. It is knowing which one to use.

Most finance professionals know roughly what they need a formula to do — pull a value from another sheet, sum figures that meet certain conditions, find the variance between two columns. The gap is often between knowing what you want and knowing the exact function and syntax that does it, especially across the differences between Excel and Google Sheets.

Claude is well suited to this gap. Describe what you want the formula to do in plain English, and Claude writes it — for either Excel or Google Sheets, with an explanation of how it works. It can also take a formula that is producing an error and explain exactly what is wrong and how to fix it.

Key insight: You do not need to know function names to use Claude for formulas. Describe the outcome you want in plain language — Claude translates that into the correct formula and explains how it works.

Write formulas from a description

Describe what you need in plain English — Claude writes the formula and explains each part.

Debug formula errors

Paste a formula that is returning an error — Claude explains what is wrong and how to fix it.

Convert between Excel and Sheets

Translate a formula written for Excel into Google Sheets syntax, or the other way round.

Excel

=XLOOKUP(A2,Sheet2!A:A,Sheet2!C:C,"Not found")

Google Sheets

=IFNA(VLOOKUP(A2,Sheet2!A:C,3,FALSE),"Not found")

These three prompts cover the most common finance formula tasks. The more specific you are about the layout of your data, the more accurate the formula will be.

Key insight: Always tell Claude whether you are using Excel or Google Sheets, and describe your data layout — which columns, which sheet names. The same logical formula often has different syntax in each tool.

Prompt 1 — Write a formula from a description

Act as a spreadsheet expert. Write a formula for [Excel / Google Sheets] that does the following: What I need: [Describe the outcome in plain English — e.g. "Look up the department name for each employee ID, and show 'Not found' if there is no match"] My data layout: - [Sheet/column where the lookup value is — e.g. "Employee IDs are in Sheet1, column A"] - [Sheet/column where the result should come from — e.g. "Department names are in Sheet2, columns A (ID) and C (Department)"] Provide: the formula, a one-sentence explanation of what it does, and a note on any cell references I will need to adjust for my actual sheet.

Prompt 2 — Debug a formula error

Act as a spreadsheet expert. The following formula is producing an error in [Excel / Google Sheets]. Explain what is causing the error and provide a corrected formula. Formula: [Paste the exact formula, including the error it shows — e.g. #N/A, #REF!, #VALUE!] Context: [Briefly describe what the formula is supposed to do and your data layout] Provide: a plain-English explanation of what is causing the error, the corrected formula, and a one-sentence explanation of what changed.

Prompt 3 — Convert a formula between Excel and Google Sheets

Act as a spreadsheet expert. Convert the following formula from [Excel / Google Sheets] to [Google Sheets / Excel], adjusting syntax as needed. Formula: [Paste the formula] Provide: the converted formula, and a one-sentence note on any functional differences between the two versions — for example, if one tool handles errors or array results differently.

Claude can produce a working formula quickly — but a formula that runs without error is not the same as a formula that is correct for your data. These habits close that gap.

Key insight: Always ask Claude to explain the formula, not just provide it. If you understand what each part does, you can spot when it does not match your actual data layout — and adjust it yourself with confidence.

Always ask for an explanation alongside the formula

A formula you understand is one you can adjust, troubleshoot and trust. Ask Claude to break down what each function and argument is doing.

Test on a small range before applying broadly

Apply a new formula to a handful of rows first and check the results manually against figures you already know, before rolling it out across a full dataset.

Be precise about your data layout

Sheet names, column letters and whether headers are included all affect the formula. The more precisely you describe your layout, the less adjustment the formula will need.

Do not paste real financial data into the prompt

You only need to describe your data layout — column positions, sheet names, what the values represent. There is no need to paste actual figures, account numbers or company names to get a working formula.

Important: Always test a Claude-generated formula against figures you can verify manually before using it in a live financial model or report. A formula that runs without error can still produce the wrong result if it does not match your data layout exactly.