百分比變化率計算器
計算兩個值之間的百分比變化率。
Calculating Percentage Increase and Decrease
Overview
Percentage change measures how much a value has grown or shrunk relative to its starting point — essential for tracking prices, metrics, and results. This calculator finds the percentage increase or decrease between two numbers instantly in your browser.
How to Use (Step by Step)
- 1
Enter the original value
The starting (old) number.
- 2
Enter the new value
The number you are comparing against the original.
- 3
Read the percentage change
A positive result is an increase, negative is a decrease.
How It Works
Percentage change = ((new value − old value) ÷ old value) × 100. A positive result is an increase, a negative one a decrease. The key is that the change is always measured against the original (old) value, which is why a rise from 50 to 100 is a 100% increase, but a fall from 100 to 50 is only a 50% decrease — the base is different each way.
When to Use This
Tracking a price rise or drop. Measuring growth in followers, sales, or traffic. Comparing this period's figure against last period's.
Frequently Asked Questions
Because percentage change is measured against the starting value. 50 to 100 is +100% (base 50), but 100 to 50 is −50% (base 100).