Everyday & industry
Percentage Increase / Decrease Calculator
Calculate percentage increase, percentage decrease and absolute change between values, apply or reverse percentage changes, or compare two percent-change scenarios.
Use this calculator to measure percentage increase or decrease between two values, or apply and reverse percentage changes.
Percentage change uses the starting value as the reference point.
Calculations run locally in your browser. Your inputs are not saved.
Choose a percentage-change calculation.
About this calculator
Absolute and Relative Change
Absolute change measures the numerical difference. Percentage change expresses that difference relative to the starting value.
- Absolute Change = Ending − Starting.
- Percentage Change = (Ending − Starting) ÷ Starting × 100.
- The starting value is the reference point. Changing the reference changes the percentage.
- Calculations retain full precision internally; displayed values are rounded only for readability.
Percentage Change Examples
These are static examples. Your calculated result appears separately after you submit your values.
- Increase from 80 to 100: absolute change 20; (100 − 80) ÷ 80 × 100 = 25%, a 25% increase.
- Decrease from 100 to 80: absolute change −20; (80 − 100) ÷ 100 × 100 = −20%, a 20% decrease.
- Increase 200 by 15%: change amount 200 × 0.15 = 30; new value 200 + 30 = 230.
- Find the original value before a 20% increase that ends at 120: 120 ÷ 1.20 = 100.
Frequently asked questions
How do I calculate percentage increase?
Subtract the starting value from the ending value, divide by the starting value, then multiply by 100. For example, 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%.
How do I calculate percentage decrease?
Use (ending − starting) ÷ starting × 100. A negative percentage is classified as a decrease, and its magnitude is displayed. For example, 100 to 80 gives −20%, displayed as a 20% decrease.
Why are percentage increase and decrease not symmetrical?
Each uses its own starting value. Going from 80 to 100 is a 25% increase, while going from 100 to 80 is a 20% decrease. The absolute change has the same magnitude, but the reference value differs.
What happens when the starting value is zero?
Percentage change from zero is undefined using the standard formula because it requires division by zero. The absolute change remains available.
How do I reverse a percentage increase?
To find the original value before an increase, divide the final value by 1 + percentage ÷ 100. A final value of 120 after a 20% increase gives 120 ÷ 1.20 = 100.
How do I reverse a percentage decrease?
Divide the final value by 1 − percentage ÷ 100. For example, 80 after a 20% decrease gives 80 ÷ 0.80 = 100. A 100% decrease cannot uniquely recover an original value. Decreases above 100% use a negative multiplier and are allowed mathematically.
What is the difference between percentage change and percentage difference?
Percentage change uses a starting/reference value and has a direction. Percentage difference treats both values symmetrically and uses their average magnitude. This Tool focuses on percentage change, applying changes, reversing changes and comparing change scenarios.
General mathematical calculations only, not financial or business advice. No accounts, database, AI or external API calls are used. Calculations run locally in your browser and your inputs are not saved.