Claude for Excel: Build and Analyze With Checks

You can use Claude for Excel work by uploading a supported workbook, asking for a specific analysis or change, and checking the returned formulas and totals in Excel. Claude can also create downloadable spreadsheets, but a convincing explanation is not evidence that every cell is correct.

Keep the workbook in its approved file location and the reasoning somewhere the next session can find it. fenbs can hold metric definitions, human decisions, review tasks, and lessons without holding the workbook data. This guide covers the analysis workflow; the Claude Excel add-in guide covers working inside Excel.

How do you start with a workbook safely?

1. Save a dated working copy. Preserve the original workbook and record which version is the source.
2. Remove information the task does not need. Check hidden sheets, comments, and supporting tabs before sharing a file.
3. Write the question, the relevant sheets, the reporting period, and the meaning of each important measure.
4. Upload the copy and ask Claude to describe its structure before doing calculations or changing anything.
5. Request one small result, verify it, and expand the task only after the source and definitions match.

Anthropic lists XLSX among its supported upload formats↗ (opens in a new tab), with code execution and file creation enabled for that format. Use the vendor page for current availability and limits. Do not assume that attaching a workbook proves the assistant inspected every sheet, formula, or embedded object.

Start with a readback: ask for sheet names, the table used, column headings, row count, date range, and any missing values. Compare those details with Excel yourself. If Claude describes only one tab when the answer depends on three, fix the scope before asking for a conclusion.

What should you put in the analysis request?

Describe the business question before requesting a formula. In a hypothetical service business, “compare revenue” could mean invoices issued, cash received, or work delivered. Specify one definition, which rows to exclude, and how refunds should be handled. An accurate calculation of the wrong definition still answers the wrong question.

Name the output as precisely as the input. Request a summary by month, a list of exceptions, or an additional calculation column. Ask the assistant to identify unclear assumptions rather than quietly choose them. The introduction to what Claude is gives broader context for the assistant behind this work.

Use only the Orders sheet in the attached working copy.
Goal: summarize monthly net revenue by service category.
Definition: invoice amount less refunds; exclude void orders.
First list the columns, row count, date range, and uncertainties.
Do not change the source data or invent missing categories.
Then propose the calculation and the checks I should run.

Once a person resolves a definition, save the answer as a decision rather than burying it in the conversation. In fenbs Decisions and rules, the next connected assistant can read that approved definition before suggesting a different calculation.

How do you build or review formulas?

Ask for the formula, the cell or table column where it belongs, and a plain explanation of its references. Request the expected result for a small example you can calculate yourself. For a lookup, include an existing key, a missing key, and a repeated key so you can see how each case behaves.

Review whether the formula points to the intended range and whether copied references move correctly. Check blank cells, zeros, negative values, and dates at the reporting boundary. Also check whether a missing value becomes an empty cell, an error, or zero. Those choices can change a report without making the formula visibly fail.

Anthropic documents file creation and editing↗ (opens in a new tab), including Excel files with formulas. If you request a revised workbook, ask for a change summary and keep inputs separate from calculated results. Open the download in Excel, recalculate, and inspect the actual formulas rather than accepting a screenshot or written assurance.

Which checks catch convincing but wrong results?

Use an independent route for an important total. If Claude provides a monthly revenue table, calculate the same total with your own simple summary in Excel. Reconcile the opening row count, included rows, excluded rows, and final amount. Two answers from the same conversation are not two independent checks.

Investigate differences before polishing the chart. Common causes include text stored as numbers, duplicate records, inconsistent category names, or a filter carried over from earlier work. Record the cause of a correction, not just the corrected total. That gives a future reviewer a concrete warning to use.

How do you handle uncertainty and repeat work?

Separate three statements: the data shows a difference, a possible explanation exists, and a person has approved an action. A sales dip does not establish its cause. Ask Claude to distinguish observations from hypotheses and to name additional evidence needed before making a recommendation.

For repeat reports, retain the checked request, the source location, and the remaining limitations. The next run still needs fresh row counts and reconciliation. If your workflow also involves local automation, Claude Code and Claude Cowork have separate guides; neither replaces checking the workbook output.

How to do this with fenbs

1. Create a free account and add a project named for the report or workbook process.
2. Record the human-approved metric definitions, exclusions, and review requirement in Decisions and rules. Keep private workbook contents out of the record.
3. Add tasks for formula review, reconciliation, and outstanding questions, with a source link where appropriate.
4. After review, record what was checked and save any correction as a lesson. Save Where we left off so the next session knows what remains.

fenbs does not calculate spreadsheets or replace Excel. It is unnecessary for a one-off formula you can verify immediately; it helps when assumptions and unfinished reviews need to survive another conversation. Browse the AI at work hub for other practical workflows, and begin with one recurring report whose definitions you already understand.