Math
Percentage Decrease Calculator
Work out how much a value has fallen in percentage terms, from an old value to a new value.
This result tells you how far the value has fallen from the old value, as a percentage of the old value.
Formula
Percentage decrease = ((old value − new value) ÷ old value) × 100.
How it works
Enter the old and new values. The calculator finds how much was lost, divides by the old value, and converts it to a percent. A positive answer means a fall.
Worked example
For example, an old value of 100 falling to a new value of 80 gives ((100 - 80) / 100) x 100 = 20.00% decrease.
FAQs
What does the Percentage Decrease do?
It takes the values you enter and works out the percentage decrease for you, showing the result straight away.
What should I enter?
Enter ordinary numbers in the boxes above. If a value does not make sense for this calculation, the page will ask you to check it instead of showing a wrong answer.
Can I use the result for homework or everyday math?
Yes. It is a general-purpose math helper; for exam or professional work, still check the steps against your own working.
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