Decrease Percent Calculator
Percentage Decrease Calculator works out Answer for the selected comparison and What the answer is from Initial / accepted / first value and Final / measured / second value. The default figures on this page give answer for the selected comparison of -50 %; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
3 steps
- Fall = 50 - 75 = -25
- Divide by the original amount: -25 / 50 = -0.5
- Multiply by 100: a decrease of -50%
Its 11 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
2 sources
What the Percentage Decrease Calculator calculates
Compares two values and reports the percentage increase or decrease from the first to the second, the symmetric percentage difference between them (which divides by the mean of the two magnitudes, not by the starting value), the percent improvement toward whichever direction is better, and the percent or relative error of a measurement against an accepted value.
How to use this Percentage Decrease Calculator
Enter Initial / accepted / first value and Final / measured / second value. Answer for the selected comparison updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Answer for the selected comparison, What the answer is and In words.
The method follows Wikipedia, "Relative change and difference" — relative change uses |x_reference| in the denominator; percentage difference uses the mean of the magnitudes and OpenStax, Chemistry 2e §1.5 "Measurement Uncertainty, Accuracy, and Precision" — percent error = |experimental - accepted| / accepted x 100.
What you can compare
Change one input at a time to see how it affects Answer for the selected comparison, What the answer is and In words. The inputs you can vary are Initial / accepted / first value and Final / measured / second value.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How do I decrease a percentage on a calculator?
Compares two values and reports the percentage increase or decrease from the first to the second, the symmetric percentage difference between them (which divides by the mean of the two magnitudes. Open “How this is worked out” beside the result to see each step for your own figures.
How to calculate a 75% reduction?
It needs Initial / accepted / first value and Final / measured / second value. Nothing else is required, and the figures stay in your browser.
What is the formula for calculating a percentage decrease?
Compares two values and reports the percentage increase or decrease from the first to the second, the symmetric percentage difference between them (which divides by the mean of the two magnitudes. On this page it is computed from Initial / accepted / first value and Final / measured / second value and shown as Answer for the selected comparison, What the answer is and In words.
How do I calculate a 10% decrease in a number?
The result gives Answer for the selected comparison, What the answer is, In words, Percentage change, Percentage increase and Percentage decrease, each labelled with its unit so the figure can be read on its own.
What information do I need for the Percentage Decrease Calculator?
You need Initial / accepted / first value and Final / measured / second value. The page opens with default figures that give answer for the selected comparison of -50 %, so you can see the scale before entering your own.
What does this Percentage Decrease Calculator show?
It shows Answer for the selected comparison, What the answer is, In words, Percentage change, Percentage increase, Percentage decrease, Absolute change (final - initial) and Percentage difference, with the working and any warnings for your entries.