Open the spreadsheet you want to protect in Excel, click the "Review" tab and then click "Protect Sheet" in the Changes group to display the Protect Sheet dialog.

With the Excel file open select File in the top-left corner of the screen, followed by Info. Select Protect Workbook, then choose Encrypt with Password.

You can have Excel make a spreadsheet in read only format for others, so that people can read its contents but not edit them, or you can enforce other content restrictions.

Working with an Excel workbook that contains confidential information such as financial data, personal details, or trade secrets? Here's how you can protect the data in your Excel file from prying ...

You worked hard to put that Excel sheet together, now protect it from unintended damage.