Enter the total decay and the original starting amount into the Calculator. The calculator will evaluate the Decay Percentage. 

Decay Percentage Formula

DP = TD / OA *100


  • DP is the Decay Percentage (%)
  • TD is the total decay
  • OA is the original starting amount

To calculate the Decay Percentage, divide the total decay amount by the original starting amount, then multiply by 100.

How to Calculate Decay Percentage?

The following steps outline how to calculate the Decay Percentage.

  1. First, determine the total decay. 
  2. Next, determine the original starting amount. 
  3. Next, gather the formula from above = DP = TD / OA *100.
  4. Finally, calculate the Decay Percentage.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

total decay = 16

original starting amount = 80