How to Calculate Percentage Increase or Decrease
Quick Answer
Percentage change = ((New Value - Old Value) / Old Value) × 100
If the result is positive, it's an increase. If negative, it's a decrease. For example, if a price goes from $80 to $100, that's a 25% increase. Use our percentage calculator for instant results.
When You Need Percentage Change
Percentage change calculations are essential for:
- Price changes — How much did a product price increase or decrease?
- Salary adjustments — What's your raise as a percentage?
- Business metrics — Revenue growth, cost reduction, user growth
- Investment returns — Portfolio gains or losses
- Discounts — How much are you saving on a sale?
The Percentage Change Formula
For Percentage Increase
When the new value is larger than the old value:
- Subtract old value from new value
- Divide by the old value
- Multiply by 100
For Percentage Decrease
When the new value is smaller than the old value, the same formula applies — the result will be negative, indicating a decrease.
Step-by-Step Examples
Example 1: Salary Increase
Your salary increased from $50,000 to $55,000.
$55,000 - $50,000 = $5,000
$5,000 / $50,000 = 0.10
0.10 × 100 = 10% increase
Example 2: Price Decrease
A product's price dropped from $80 to $60.
$60 - $80 = -$20
-$20 / $80 = -0.25
-0.25 × 100 = -25% (25% decrease)
Common Use Cases
Business Growth
Revenue grew from $100,000 last year to $150,000 this year. That's a 50% increase — a strong growth indicator for investors and stakeholders.
Cost Reduction
Operating costs decreased from $40,000 to $32,000. That's a 20% reduction, showing improved efficiency.
Retail Discounts
An item was $200, now $150. The discount is 25% off — useful for marketing and customer communication.
Investment Performance
Portfolio value changed from $10,000 to $11,500. That's a 15% gain on your investment.
Old price $100 → New price $120: 20% increase
Old price $100 → New price $80: 20% decrease
Old price $100 → New price $50: 50% decrease
Percentage Increase vs Percentage Of
These are different calculations:
Percentage Increase
How much did something grow relative to its original value?
Example: Sales went from 100 to 150. That's a 50% increase.
Percentage Of
What portion is one value of another?
Example: 150 is 150% of 100 (not the same as increase).
Common mistake: Saying "sales increased by 150%" when they went from 100 to 150. The increase is 50%, not 150%. The new value (150) is 150% of the old value.
Reversing Percentage Changes
If something increased by 20%, you can't simply decrease by 20% to get back to the original:
Start: $100
After 20% increase: $100 × 1.20 = $120
After 20% decrease: $120 × 0.80 = $96 (not $100!)
To reverse a percentage increase, you need a different percentage decrease. To reverse a 20% increase, you need a 16.67% decrease.
Common Mistakes to Avoid
- Using the wrong base — Always divide by the original (old) value, not the new value
- Forgetting to multiply by 100 — The formula gives a decimal; convert to percentage
- Confusing increase with "percentage of" — A 50% increase means the new value is 150% of the old
- Negative results — A negative percentage indicates a decrease, not an error
- Percentage points vs percent — Going from 10% to 15% is a 5 percentage point increase, but a 50% relative increase
Using the Percentage Calculator
For quick and accurate calculations, use our percentage calculator. It handles:
- Percentage increase and decrease
- Finding what percentage one number is of another
- Calculating a specific percentage of a number
- Reverse percentage calculations
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