arithmetic
Percentage Increase and Decrease
January 17, 2026
6 min read
PanMaths Team
⚡ THE FORMULA
The difference between values divided by the original value, then multiplied by 100.
((New - Old) / Old) × 100← THE FORMULA
What is Percentage Change?
Percentage change is a way to express a change in a value as a percentage of the original value. Whether it's a price hike, a population growth, or a weight loss, understanding how much something has changed in relative terms is essential for clear communication and analysis.
How to Calculate Percentage Increase
1
Find the difference
Subtract the original value from the new value.
2
Divide by original
Divide that difference by the starting (original) number.
3
Convert to percentage
Multiply the resulting decimal by 100 and add the % sign.
💡Pro Tip: Direction Matters
- If the result is positive (+), it is a percentage increase.
- If the result is negative (-), it is a percentage decrease (usually expressed as a positive number for 'decrease').
- Always ensure your 'Original' value is truly the starting point of the change.
Real-World Example
A $50 shirt goes on sale for $40 = 20% DecreaseCalculation: ((40 - 50) / 50) x 100 = -20%
Rent goes from $1200 to $1320 = 10% IncreaseCalculation: ((1320 - 1200) / 1200) x 100 = +10%
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