Percentage Calculator
Calculate a percent of a value, percent increase or decrease, and percentage change.
What this tool does
Find a percentage of a number, apply a percent increase or decrease, or calculate percentage change between two values.
How to use
- Choose % of, Increase, Decrease, or Change.
- Enter the values for that mode.
- Copy or share the result. Change mode uses old and new values.
Formula
% of: value × (percent ÷ 100). Change: ((new − old) ÷ old) × 100
Examples
15% of 200
Input: value=200, percent=15, mode=of
Output: 30
200 × 0.15 = 30.
Price from $40 to $50
Input: old=40, new=50, mode=change
Output: 25% increase
(($50 − $40) ÷ $40) × 100 = 25%.
Common use cases
- Calculate sales tax amounts
- Measure percent increase or decrease
- Compute percentage change between two metrics
FAQ
How do I calculate percentage change?
Use Change mode. Enter the old value and the new value. The formula is ((new − old) ÷ old) × 100.
Why is a 50% drop not recovered by a 50% rise?
After a 50% drop the baseline is smaller, so you need a 100% increase to return to the original value.
What if the old value is zero?
Percentage change from zero is undefined because you cannot divide by zero. Use the absolute difference instead.
Is this financial advice?
No. This is a simple math calculator for estimates.
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Last reviewed: 2026-05-23