CalculateY
Quick Answer
A change from 80 to 100 is a 25% increase. A change from 100 to 80 is a 20% decrease. The percentage differs because the base value changes.
Percentage Change
What is X% of Y?
X is what % of Y?
Common Examples
| Input | Result |
|---|---|
| From 80 to 100 | 25% increase |
| From 100 to 75 | 25% decrease |
| From 50 to 125 | 150% increase |
| From 200 to 180 | 10% decrease |
How It Works
Three standard percentage formulas:
| Percentage Change = ((New Value − Old Value) / | Old Value | ) × 100 |
X% of Y = (X / 100) × Y
X is what % of Y = (X / Y) × 100
Where:
- A positive percentage change indicates an increase
- A negative percentage change indicates a decrease
- Division by zero is undefined (original value or whole cannot be 0)
Worked Example
A product’s price increases from $80 to $100. Percentage change = (($100 - $80) / $80) × 100% = ($20 / $80) × 100% = 25% increase. Note that a reverse change from $100 to $80 is only a 20% decrease, because the base value is now $100: ($80 - $100) / $100 × 100% = -20%.
Related Calculators
Frequently Asked Questions
What is the difference between percentage change and percentage difference?
Percentage change measures the change from one specific value to another (e.g., old price to new price) and has a direction (increase or decrease). Percentage difference compares two values without a defined direction, using their average as the base.
Can percentage change exceed 100%?
Yes. A value that doubles has a 100% increase. A value that triples has a 200% increase. There is no upper limit for percentage increases, though decreases cap at −100% (the value reaching zero).
Why does the calculator update instantly?
Because these are simple, fast calculations with only two inputs each. There's no reason to make you click a button. Results appear as soon as both fields have values.