Enter the old value in one cell and the new value in another cell
Use the formula `=(New Value-Old Value)/Old Value`
Format the result cell as Percentage
If old value is in A1 and new value is in B1, use `=(B1-A1)/A1`
To calculate increase, the result will be positive
To calculate decrease, the result will be negative
To avoid errors, make sure the old value is not zero
Copy the formula down to calculate percent change for multiple rows