Excel Course: Conditional Formatting
As you can tell from its name, conditional formatting (abbreviated CF) is formatting that is applied under particular conditions.
Let's begin with a few "ready to use" CF examples.
Select the target cells and choose the CF "Greater than...":

Enter a limit value (in this case, 50'000) and choose a format.

The formatting will now be applied to all values greater than 50'000.

If you choose the "Top 10 Items..." CF, the formatting will be applied to the 10 highest values in the cell range.

You can select the number of values to highlight (in this case, 5) as well as their formatting.

Now the 5 highest values have been formatted following your instructions.

Example using data bars:

Example using color scales:

Example using icon sets:
