What is Percentage Change?
Percentage change is the most versatile of all percentage calculations. It measures the relative difference between any two values — an old value and a new value — and expresses that difference as a percentage of the original. Unlike percentage increase or percentage decrease, it works in both directions: a positive result means the value went up; a negative result means it went down.
Percentage change is the backbone of data analysis, reporting, and comparison. Whether you're a student comparing test scores, a business analyst reviewing quarterly revenue, a scientist tracking concentration changes, or a personal finance enthusiast monitoring your savings growth, percentage change gives you the clearest, most comparable picture of how things are evolving over time.
The Percentage Change Formula
📐 Percentage Change = ((New Value − Old Value) ÷ |Old Value|) × 100
The vertical bars around "Old Value" indicate absolute value — this ensures the formula works correctly even if the old value is negative. A positive result = increase; a negative result = decrease; zero = no change.
Step-by-Step Calculation
Step 1: Identify your two values — the old (original/before) value and the new (current/after) value.
Step 2: Subtract the old value from the new value to find the change amount.
Step 3: Divide that change by the absolute value of the old value.
Step 4: Multiply by 100 to convert to a percentage.
Example: Sales Performance
Q1 revenue: $245,000 | Q2 revenue: $289,100
Change: 289,100 − 245,000 = 44,100
Ratio: 44,100 ÷ 245,000 = 0.18
Result: 0.18 × 100 = +18% increase
When to Use Percentage Change vs. Other Tools
Use Percentage Change when you have an old and new value and want to see the direction and magnitude of change in one number. Use Percentage Increase or Percentage Decrease when you already know the direction and want specialized phrasing. Use Percentage Difference when there's no inherent "before" or "after" — just two comparable values.
Handling Negative Base Values
Percentage change with negative starting values can produce counterintuitive results. If a company reports a net loss of −$100,000 in Year 1 and a loss of −$50,000 in Year 2, the percentage change is (−50,000 − (−100,000)) ÷ 100,000 × 100 = +50%. This is positive, correctly indicating improvement despite still being in the red. Always consider context when interpreting results involving negative values.
| Old Value | New Value | Change | % Change |
|---|---|---|---|
| 100 | 120 | +20 | +20% |
| 100 | 80 | −20 | −20% |
| 400 | 300 | −100 | −25% |
| 1,200 | 1,500 | +300 | +25% |
| 50 | 50 | 0 | 0% |