The percentage increase is worked out by taking the difference between the original amount and the final amount, and then dividing that difference by the original amount. This is a simple calculation that requires just a basic calculator. A writing utensil and scratch paper may be useful for recording your results.

**Find the difference between the amounts**Find the difference between the starting amount and the final amount. For example, if the original amount was 20 and the new number is 28, you would perform the following calculation: 28 - 20 = 8. You should always get a positive number. If the number is negative, then there is either a decrease in the two amounts or you used the incorrect amount.

**Divide the difference by the original**Divide the difference of the two numbers by the original. This usually produces a decimal, unless the increase is a factor of the original value. For example, if you were to use the numbers from the previous step, the process would look like this: 8 / 20 = 0.40.

**Multiply by 100**Multiply the decimal number by 100 to get the percentage increase. Using the same numbers as in the previous examples, 0.40 x 100 = 40 percent. Remember to keep the decimal spaces consistent throughout your calculations.