In this tutorial, it provides some examples and formulas to tell you how to calculate percentages in Excel. You can click below list to quickly jump to the part you need:
0:00 Introduction
0:20 Get the percentage of a given total
0:52 Get the percentage of unknown total
1:28 Get the percentage of change between two numbers
1:58 Get the total by given amount and percentage
2:13 Get the amount by given total and percentage
2:33 Increase a number by a percentage
2:49 Decrease a number by a percentage