How to Read a Spreadsheet Someone Else Built

You open a spreadsheet someone else built, maybe a predecessor who left the company, maybe a colleague who is out this week, and it looks nothing like a sheet you would have built yourself. Column headers are abbreviated. There is a tab called "working" and another called "working v2 final." Some cells have formulas, some have typed-in numbers that look like formulas used to be there. None of this means the sheet is broken. It usually means one thing: you are reading someone else's shortcuts without the context that made them make sense at the time.

Start with the shape, not the numbers

Before reading a single value, look at the shape of the workbook: how many tabs, what each tab is roughly named, and which tab looks like the actual data versus a summary or a scratch area. Most inherited spreadsheets have one or two tabs doing the real work and several others that are dead ends, leftover drafts, or one-time calculations nobody deleted. Spend two minutes just clicking through tabs before you commit to reading any of them closely.

Find where the real data actually starts

Inherited sheets are especially prone to the quiet problems that hide what data is telling you: a header row that is not actually row 1, a few blank rows used as a divider partway down, or a column that looks numeric but is stored as text because it was pasted in from another system. Before you trust any total on the sheet, confirm the range it is actually summing matches the range you think has data in it. If text is quietly mixed into a number column, MySheetAI's answer on trimming and cleaning pasted text (mysheetai.com/answers/trim-clean) covers the exact fix.

Trace one formula end to end

Pick the one cell that matters most, usually whatever total or result someone is going to ask you about, and trace its formula back as far as it goes. In Excel, Ctrl+` (or Formulas > Show Formulas) reveals every formula on the sheet at once instead of one cell at a time, which is faster than clicking through cells individually. Google Sheets has the same view under View > Show formulas. You are looking for two things: what the formula actually references, and whether that reference still points at something reasonable. A VLOOKUP or INDEX/MATCH pointing at a range that no longer covers all the data is one of the most common silent breaks in an inherited sheet; MySheetAI's guides on VLOOKUP (mysheetai.com/answers/vlookup) and IFERROR (mysheetai.com/answers/iferror) are useful references if the formulas you find are unfamiliar or throwing errors you cannot explain.

Ask what the sheet owner would tell you

• What number does this sheet exist to answer? Every inherited sheet was built to answer something specific, even if that purpose got buried under later additions.
• What would this person warn me about if they were handing the sheet over in person? Usually it is one known quirk: a tab that is out of date, a formula that needs a manual refresh, or a number that is an estimate, not a fact.
• What have I not touched yet? List the tabs and ranges you have not reviewed so you know what you are still trusting blind.

When it is faster to ask a tool instead

Tracing formulas cell by cell is slow, and it is easy to miss a broken reference buried three tabs deep. MySheetAI's upload feature reads an inherited spreadsheet and reports back what it finds in plain English, including the kind of quiet structural issues described above, without you needing to hunt through every tab by hand. A free account includes one detailed analysis a week (up to 3MB), and Pro removes that limit for $12 a month or $100 a year. Either way, the formula-tracing skill above is worth having, since it is exactly what you will need for the parts of the sheet a tool cannot guess the intent behind.