To calculate a percentage of a number: `=A1*B1`
To calculate what percentage one value is of another: `=A1/B1`
To format a result as a percentage: select the cell and click `%` or use `Ctrl+Shift+%`
To increase a value by a percentage: `=A1*(1+B1)`
To decrease a value by a percentage: `=A1*(1-B1)`
To calculate percentage change: `=(B1-A1)/A1`
To calculate percentage difference: `=ABS(A1-B1)/AVERAGE(A1,B1)`
To convert a decimal to a percentage: multiply by 100 or format as `%`
To calculate percentage of total: `=A1/SUM($A$1:$A$10)`
To calculate percentage points difference: `=B1-A1`