Why Numbers Don’t Calculate in Excel
Numbers that look correct but won’t sum or compare are almost always text in disguise. Learn how to diagnose and fix text-as-number problems with VALUE and CLEAN.
Data Cleaning
April 2026
Lookup
Why VLOOKUP Gets Slow in Large Excel Workbooks
VLOOKUP slows down as data grows because of full column references and repeated lookups. Learn the real causes and how to fix performance without changing your logic.
Excel Functions
How to Calculate OR Conditions Correctly With SUMIFS
SUMIFS only supports AND logic between criteria. Learn why OR conditions silently fail and the correct pattern for summing East AND (Online OR Phone) sales.
Errors
Why Overusing IFERROR Breaks Excel Reports
IFERROR makes reports look clean but can hide real problems. Learn when IFERROR helps, when it breaks logic, and how to use it safely with a three-layer strategy.
Excel Functions
What Makes a Small Set of Excel Functions Dominate Real‑World Work
The same handful of Excel functions appear in nearly every workbook. Learn the five roles they fill and why they survive while rarer functions don’t.
Data Cleaning
Why Text and Numbers Don’t Separate Cleanly in Excel
Mixed text and numbers in one cell silently break SUM,sorting, and lookups. Learn how to separate them reliably with VALUE and SUBSTITUTE.
Excel Functions
Why Date Calculations Go Wrong in Excel Reports
DATEDIF and EOMONTH look simple but fail on edge cases like reversed dates and month-end starts. Learn how to use them correctly in contract and billing calculations.
Data Cleaning
Why Duplicate Data Keeps Appearing in Excel
Removing duplicates once does not stop them from coming back. Learn three methods — Conditional Formatting, Remove Duplicates, and UNIQUE — and when to use each.
Excel Functions
Why Conditional Data Extraction Breaks in Excel Reports
Manual filtering and copy-pasting create stale snapshots. Learn how the FILTER function builds live, condition-based tables that update automatically.
Excel Functions
How Dynamic Lists Cause Errors in Traditional Excel Reports
Manual copy-paste lists go stale the moment data grows. Learn how UNIQUE and SORT build self-updating lists that never need to be redone.