Percentage Change Calculator: Master Growth & Decline Calculations

What is Percentage Change?

Percentage change measures how much a value has increased or decreased relative to its starting point, expressed as a percentage. It's the most common way to compare changes over time because it accounts for the initial value.

For example, a $10 increase means something different if the original value was $100 versus $1,000. Percentage change captures this context automatically.

Percentage Change Formula

The core formula for calculating percentage change is:

Key Points:

• Positive result = Increase or growth
• Negative result = Decrease or decline
• Larger absolute value = Larger change

Real-World Percentage Change Examples

Example 1: Stock Price Growth

Scenario: A stock you own increased from $50 to $65

• Change = $65 − $50 = $15
• Percentage Change = ($15 ÷ $50) × 100 = 30% increase
• Your investment grew by 30%

Example 2: Sales Decline

Scenario: Monthly sales dropped from $10,000 to $8,500

• Change = $8,500 − $10,000 = −$1,500
• Percentage Change = (−$1,500 ÷ $10,000) × 100 = −15% decline
• Sales fell by 15%

Example 3: Salary Increase

Scenario: Your salary increased from $45,000 to $52,000

• Change = $52,000 − $45,000 = $7,000
• Percentage Change = ($7,000 ÷ $45,000) × 100 = 15.56% increase
• Your salary grew by approximately 15.56%

Common Percentage Change Scenarios

Why Percentage Change Matters

1. Comparing Across Different Scales

A $100 increase on a $500 item (20%) is different from a $100 increase on a $10,000 item (1%). Percentage change shows the true impact.

2. Year-Over-Year Growth Tracking

Businesses use percentage change to track growth: "Revenue grew 23% year-over-year" is more meaningful than absolute numbers.

3. Investment Performance

Investors compare returns using percentage change: "My stock gained 15%" is clearer than "I made $3,000."

4. Inflation & Economic Indicators

Economists track inflation rates, unemployment changes, and GDP growth all as percentage changes.

Common Mistakes in Percentage Change

Mistake 1: Using New Value as the Base

❌ Wrong: ($65 − $50) ÷ $65 = 23.1% ✅ Correct: ($65 − $50) ÷ $50 = 30%

Always divide by the original (starting) value, not the new value.

Mistake 2: Reversing the Subtraction

❌ Wrong: ($50 − $65) ÷ $50 = −30% means it decreased (but it increased!) ✅ Correct: ($65 − $50) ÷ $50 = +30% correctly shows growth

Mistake 3: Forgetting to Multiply by 100

If you forget the ×100 step, you get a decimal (0.30) instead of a percentage (30%).

Quick Percentage Change Tips

The 50% Rule

50% change means the new value is half (decrease) or double (increase) the original.

The 10% Shortcut

Calculate 10% first by moving the decimal left, then multiply to find other percentages.

The Proportion Method

If the original was 100 units, the new value tells you the percentage directly:

• Original: 100, New: 130 = +30% change
• Original: 100, New: 75 = −25% change

Percentage Change in Your Daily Life

• Shopping: "This item is 20% off" = 20% change
• Fitness: "I increased my workout by 15%" = 15% change
• Grades: "My test scores improved 18%" = 18% change
• Finance: "My savings grew 5% this year" = 5% change
• Health: "Blood pressure decreased 12%" = 12% change

The Bottom Line

Percentage change is straightforward once you master the formula:

• Formula: ((New − Old) ÷ Old) × 100
• Always divide by the original value - This is the critical step
• Positive = increase, Negative = decrease - Sign tells you the direction
• Use tools to verify - Our percentage change calculator prevents errors

Ready to track change accurately? Use our percentage change calculator for instant, reliable results.

Related Calculators

• Percentage Points Calculator - Learn the difference between percentage change and points
• Percentage Difference Calculator - Compare two values symmetrically
• All Percentage Calculators - Master every type of percentage calculation

Happy calculating!