Steps
- Select the cells to validate - Highlight the range where the rule should apply - for example a column where users enter a status or quantity.
- Open Data > Data Validation - On the Data tab, click Data Validation to open the Settings dialog.
- Choose an Allow type - Pick List for a dropdown, Whole number or Decimal for number ranges, Date for date limits, Text length for size limits, or Custom for a formula.
- Enter the criteria - For a dropdown, type comma-separated options or reference a range like =Sheet2!$A$1:$A$10. For ranges, set the minimum and maximum.
- Add an input or error message - Use the Input Message tab to show a hint and the Error Alert tab to block or warn on invalid entries, then click OK.
Before You Start
- Reference a range or named range for dropdown sources so the list updates when you add options.
- Enable 'Ignore blank' if empty cells should be allowed.
- Custom-formula rules must return TRUE for valid entries, e.g. =A1>0.
Alternative Methods
- Generate the rule online - Use the Data Validation helper to configure a dropdown, number, date, text-length, or custom rule and copy the exact source string and steps into Excel.
- Dependent dropdown lists - Combine named ranges with INDIRECT to make one dropdown's options depend on another cell's selection.