Use the formula `=(New Value-Old Value)/Old Value`
Format the result cell as Percentage
Example: `=(B2-A2)/A2`
To calculate increase, use the same formula
To calculate decrease, use the same formula
If the old value is in `A2` and the new value is in `B2`, enter `=(B2-A2)/A2`
Copy the formula down to apply it to more rows
Handle zero old values to avoid errors, using `=IF(A2=0,””,(B2-A2)/A2)`