Percentage Decrease Calculator
Enter an original value and a new value to calculate how much the value decreased and the decrease as a percentage of the original.
- Absolute Decrease
- 20
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The result measures the reduction relative to the original value. It is not automatically the inverse of the same percentage increase.
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How to Use This Calculator
Enter the old value first and the new value second. The old value must be greater than zero.
Formula & Methodology
Absolute Decrease = Old Value − New Value. Percentage Decrease = ((Old Value − New Value) ÷ Old Value) × 100.
Example: a price falls from $100 to $80
The absolute decrease is $20. The percentage decrease is ($20 ÷ $100) × 100 = 20%.
The old value must be greater than zero. If the new value is above the old value, the result is negative; use Percentage Increase or Percentage Change instead.
This calculator provides a mathematical comparison only. Confirm the inputs before using the result for pricing, budgeting, or reporting.
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Related Guides
- Reverse Percentage Explained: Find the Original Value Before a % ChangeLearn how to calculate the original value before a percentage increase or decrease. Covers the reverse percentage formula with worked examples in prices, discounts, and taxes.
- What Is Percentage Increase? Formula, Examples, and Common UsesUnderstand percentage increase: the formula, how to calculate it step by step, and real-world examples in prices, salaries, and test scores. Includes common mistakes to avoid.
- Percentage Difference vs. Percentage Change: What's the Difference?Percentage difference and percentage change are not the same thing. Learn when to use each, how to calculate both, and why the distinction matters in data analysis and everyday math.
- How Percentages Work: Complete Guide with ExamplesUnderstand percentages from the ground up. Covers what percent means, basic percentage calculations, percentage increase and decrease, and common real-world uses.
- How to Calculate Percentages Without a Calculator: Mental Math MethodsLearn to calculate percentages in your head using simple strategies: the 10% shortcut, doubling/halving, and breaking percentages into parts. Works for tips, discounts, and sales.
Frequently Asked Questions
- How do you calculate percentage decrease?
- Subtract the new value from the old value, divide by the old value, and multiply by 100.
- Is a 20% decrease the reverse of a 20% increase?
- No. The reference value changes. A 20% increase from 100 gives 120, while a 20% decrease from 120 gives 96.
- What does a negative decrease mean?
- It means the value increased rather than decreased. Use the Percentage Increase or Percentage Change Calculator.
- Can a percentage decrease exceed 100%?
- For ordinary nonnegative values, a drop to zero is a 100% decrease. A result above 100% usually means the new value is negative.
Last updated 7/17/2026