Reverse Percentage Calculator

Enter a number and the percentage of a number and this reverse percentage calculator will determine the original number. For example 25% of X is 5. Solving for X we find the the answer to be 4.

Percentages are numbers that are expressed as fractions. They are denoted by the symbol %. These numbers have no units and are there for dimensionless. For example, the percentage 25% is equal to a fraction of 1/4 and can be written as .25. The concept of percents and fractions have been around for centuries. In ancient Rome there were often calculations performed using multiple of 1/100 which is the same as using decimals to describe a fraction.


Below are two different examples of how to calculate numbers from percentages, or otherwise known as reverse percentage.

  1. Let’s assume we a have a number 100. We find that this number is 25% of some original number. To determine the orginal number, we simply need to multiply 100 by the inverse of the equal fraction to 25%. So, 25%= 1/4 and the inverse of 1/4 = 4. Therefore the original number can be calculate as 100*4=400.
  2. In this example we are going to use a more abstract number and percent. Say we have a number that is some percent of another number. We will assume our number is 121 and that is 32% of another number X. To calculate x we must use the same process as the previous example. 121 * 100/32 (the inverse of .32). = 378.125.
reverse percentage calculator
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