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Percentage change measures how much a value has grown or shrunk relative to its starting point — used everywhere from tracking price changes to measuring business growth.
This calculator finds the percentage increase or decrease between an old and new value and shows the full working.
How it works
Enter the old (starting) value and the new (ending) value. The calculator finds the difference between them, divides it by the absolute value of the old value, and multiplies by 100 to get the percentage change.
- Enter old value.
- Enter new value.
- Click Calculate to see your results.
Examples
A price increase
A price rising from $50 to $65 is a 30% increase, since the $15 difference is 30% of the original $50.
A weight decrease
A value dropping from 200 to 150 is a 25% decrease, since the -50 difference is -25% of the original 200.
Who should use it
- Tracking how much a price, salary, or metric has grown or shrunk over time.
- Comparing performance between two periods in a business report.
Industry applications
- Finance and business reporting
- Retail pricing and e-commerce analytics
Advantages
- Clearly labels the result as an increase, decrease, or no change.
- Handles both positive and negative old and new values correctly.
Limitations
- Cannot calculate a percentage change from a starting value of zero, since that is mathematically undefined.
Common mistakes to avoid
- Dividing by the new value instead of the old value, which gives a different (and less standard) result.
- Forgetting that a negative percentage change means a decrease, not an error.
Best practices
- Always be clear about which value is the "old" (starting) value and which is the "new" (ending) value before calculating.
Tips
- A percentage change of over 100% simply means the value more than doubled — it's not an error.