Who this site is for
Excel Function Mastery is for people who use spreadsheets as part of their work rather than as their main job: analysts maintaining a monthly report, small business owners tracking sales, administrators cleaning up lists, and students working through an assignment. It assumes you can enter a formula, but not that you know every function or remember the exact syntax.
The site is run independently and is not affiliated with Microsoft. It focuses on a small set of browser tools that each solve a defined problem, plus a sample workbook you can download and inspect.
Which tool do I need?
- A formula someone else wrote is hard to follow.
- Use the Formula Explainer. Splits the formula into numbered steps and shows which part Excel calculates first.
- A cell shows #N/A, #VALUE!, #REF!, #DIV/0! or #SPILL!.
- Use the Excel Error Decoder. Explains the error code and lists the likely causes in the order to check them.
- You are not sure whether to use VLOOKUP, XLOOKUP or INDEX/MATCH.
- Use the Lookup Function Chooser. Six yes-or-no questions lead to a recommendation and a sample formula.
- You need a summary by region, month or product.
- Use the Pivot Table Planner. Plan the Rows, Columns, Values and Filters and get warnings before you build.
- You want to highlight rows, duplicates or overdue dates.
- Use the Conditional Formatting Builder. Generates the rule formula with correctly anchored references.
- A formula has to move between Excel and Google Sheets.
- Use the Formula Converter. Rewrites the functions that differ and flags those with no equivalent.
Guides
Why VLOOKUP Returns #N/A: 6 Causes and How to Test for Each
Test six common causes, apply the matching fix, and download the companion workbook.
Why SUMIFS Returns 0: 6 Causes and How to Fix Each
Find your cause with one COUNTIFS test, apply the fixed formula, and download the companion workbook.
Why INDEX MATCH or XLOOKUP Returns the Wrong Value: 6 Causes
Spot six silent lookup mistakes, apply the fix for each, and download the companion workbook.
Why Your IF Formula Returns the Wrong Result: 6 Causes and Fixes
Check six reasons an IF test answers the wrong question, apply the fix, and download the companion workbook.
Why COUNTIF Counts Wrong: 6 Causes and How to Fix Each
Six causes of a wrong COUNTIF count, a test for each, the fixed formula, and the companion workbook.
The sample workbook
The free sample workbook is a small, complete Excel file with five sheets: a README, an Assumptions sheet of named inputs, a Data sheet stored as an Excel Table, a twelve-month Forecast built entirely from formulas, and a Dashboard that links back to the calculations. You can change an input and watch the forecast and dashboard update.
It is useful for trying the tools on formulas that already work: paste a Forecast formula into the Formula Explainer, or plan a PivotTable from the Data sheet.
Your data stays in your browser
The tools run in your browser. You do not need an account, and formulas and inputs are processed on your device instead of being uploaded to a server. The site uses standard analytics and advertising scripts, described in the privacy policy.