A number format in Excel is a special code that controls how a number is displayed on the worksheet. For example, the number 0.51 can be displayed as 51% with the number format:
The date January 1, 2021 can be displayed as "1-Jan-20" with the number format:
The most important thing to understand about number formats is that they control the display of numbers only – number formats have no effect on underling numeric values. There are quite a few number formats built into Excel, including:
You can apply number formats from the Home tab of the ribbon:
Excel also allows custom number formats. For a more complete description of custom number format codes see: Custom Number Formats.