Math & Scientific
Percentage Decrease Calculator
Compare a strictly positive original value with a new value using percentage decrease = (original − new) ÷ original × 100. The result identifies an increase, decrease or no change. The form takes two values; it does not take an amount and a percentage rate.
Percentage Decrease Calculator helps you solve a percentage question. Enter your original value and new value and it returns the answer instantly, right in your browser with nothing uploaded.
About this calculator
Compare a strictly positive original value with a new value using percentage decrease = (original − new) ÷ original × 100. The result identifies an increase, decrease or no change. The form takes two values; it does not take an amount and a percentage rate.
How to use
- Enter a strictly positive original value and a finite new value. Zero or negative original values are outside this ordinary percentage-change model.
- Press Calculate to run the percentage decrease calculator.
- Read the result: the percentage decrease and the absolute change.
- Press Reset to clear the percentage decrease calculator and start again.
Why use Percentage Decrease Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Based on standard, well-established formulas.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Use it when working through problems
Use it for verifying answers from a textbook
Use it when preparing worksheets
Percentage Decrease in statistics and data coursework
Percentage Decrease in research and report calculations
Use it for science-fair and project numbers
Technical notes
Compare a strictly positive original value with a new value using percentage decrease = (original − new) ÷ original × 100. The result identifies an increase, decrease or no change. The form takes two values; it does not take an amount and a percentage rate.
Inputs are taken exactly as entered, so check for typos before trusting an answer.
Because it runs locally, results appear instantly with no server round-trip.
Worked example
Going from 100 down to 80: the decrease is (100 − 80) ÷ 100 × 100 = 20 ÷ 100 × 100 = 20%. Note that a 25% increase followed by a 20% decrease returns you to the start, because the base value differs each time.
FAQ
How is a percentage decrease calculated?
For a decrease from a positive original value, use (original − new) ÷ original × 100. Going from 100 to 80 is a 20% decrease.
What do I enter in the Percentage Decrease Calculator?
Enter a strictly positive original value and the new value. A zero or negative starting base is rejected; a negative new value is allowed and represents a decline through zero.
What does a 20% decrease look like?
Going from 100 to 80 is a 20% decrease.
Does the Percentage Decrease Calculator send my data to a server?
No — the Percentage Decrease Calculator runs entirely in your browser, so the numbers you enter never leave your device.