1

Subtract the first value from your second value. For example, if you wanted to know the percent difference between 80 and 85, you would subtract 80 from 85 to get 5. If the second value is smaller than your second value, you will get a negative value, which means you will have a negative percent difference.
2

Divide the result from Step 1 by the first number. Continuing the example, you would divide 5 by 80 to get 0.0625.
3

Multiply the result from step 2 by 100 to convert the number from a decimal to a percentage. Finishing the example, you would multiply 0.0625 by 100 to get 6.25 percent.