Mathematics · Algebra
Percentage Change Calculator
Calculate the percentage increase or decrease between an original and a new value.
Inputs and results stay in this browser. Change one value at a time to explore the relationship.
Calculation steps
- Difference = 100 − 80 = 20.
- Divide by |80| and multiply by 100.
- Percentage change = 25%.
Definition and formula
The difference is compared with the magnitude of the original value so the result describes change relative to the starting point.
Percentage change = (new − original) ÷ |original| × 100%
Worked example
From 80 to 100, the change is 20; 20 ÷ 80 × 100 = 25% increase.
Common mistake
Divide by the original value, not the new value.
How to learn with this calculator
Begin with the worked example, then change one value while keeping the others fixed. Compare the new result and calculation steps to identify which part of the formula changed.
Clear answers
Frequently asked questions
What does the Percentage change do?
Calculate the percentage increase or decrease between an original and a new value.
How does the Percentage change work?
The calculator applies Percentage change = (new − original) ÷ |original| × 100%. The difference is compared with the magnitude of the original value so the result describes change relative to the starting point.
What can I learn from the Percentage change?
It connects the mathematical rule to your chosen numbers and shows each calculation step. Change one input at a time to see how the result responds.
Does MW SysArc receive or store what I enter?
No. The calculation runs locally in your browser. MW SysArc does not receive or store your calculation inputs.
How should I use the result?
Use the steps to understand the method, then verify important school or professional work using the notation and rounding rules required in your setting.
Last reviewed 2026-07-14. Calculations tested 2026-07-14.