Percentage Increase / Decrease Calculator
Calculate percentage change
This calculator helps you quickly calculate the percentage increase or decrease between two values.
It is widely used in finance, ecommerce, pricing, analytics, and everyday calculations.
Understanding percentage change is essential for tracking growth, comparing values, and making better decisions.
Whether you're analysing sales performance, price changes, or investment returns, this tool provides instant and accurate results.
If you are comparing sponsor or household income between an older tax year and a lower current-year estimate for Student Finance Wales or England, use the Household Income Drop Calculator (guidance only).
Understanding your result
A positive result means an increase, while a negative result means a decrease.
The percentage is always calculated relative to the original value, not the new value.
This makes it a powerful way to compare changes over time or between values.
How the calculation works
Formula: ((New − Old) ÷ Old) × 100
The calculator measures the difference between the two values and expresses it as a percentage of the original value.
Why percentage change matters
- Track growth: Measure increases in revenue or performance
- Analyse pricing: Understand discounts and markups
- Compare results: Standardise comparisons across values
- Make decisions: Identify trends and improvements
Examples
Example 1:
£100 → £120 = 20% increase
Example 2:
£80 → £60 = 25% decrease
Example 3 (Business):
Sales increase from £5,000 to £6,500 = 30% growth
Example 4 (Discount):
£50 reduced to £40 = 20% decrease
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Frequently asked questions
How do I calculate percentage increase?
Subtract old from new, divide by old, multiply by 100.
What is percentage decrease?
Same formula but result is negative.
Can you calculate from zero?
No, division by zero is not possible.