Data Validation in Excel: Building Bulletproof Input Forms

Data validation is Excel's first line of defense against bad data. It prevents errors before they happen rather than fixing them afterward.

Why Data Validation Matters

In shared workbooks, users will inevitably enter inconsistent data: misspelled names, invalid dates, out-of-range numbers. Data validation stops this at the source.

Common Validation Types

• Dropdown lists from ranges
• Date restrictions
• Number ranges
• Custom formula validation

Custom Formula Validation Example