How to Calculate Percentage Change (Formula + Examples)

Percentage change tells you how much a value has increased or decreased relative to its starting point. It’s used everywhere — from stock market returns to salary negotiations to scientific data.

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The Percentage Change Formula

% Change = ((New Value − Old Value) ÷ |Old Value|) × 100

Positive result = increase
Negative result = decrease
Use absolute value (|Old Value|) so direction comes from the sign

Examples

Example 1 — Price Increase
A product goes from $80 to $96.
% Change = ((96 − 80) ÷ 80) × 100 = (16 ÷ 80) × 100 = +20%

Example 2 — Stock Drop
A stock falls from $150 to $127.50.
% Change = ((127.50 − 150) ÷ 150) × 100 = (−22.50 ÷ 150) × 100 = −15%

Example 3 — Salary Negotiation
You earn $55,000 and want $65,000.
% Change = ((65,000 − 55,000) ÷ 55,000) × 100 = (10,000 ÷ 55,000) × 100 = +18.2%

Percentage Change vs Percentage Difference

These are often confused:

Percentage Change — Compares a new value to an old value (direction matters: old → new).
Percentage Difference — Compares two values with no “before/after” relationship. Formula: |A − B| ÷ ((A + B) / 2) × 100

Common Real-World Uses

Investing — Calculate portfolio returns, stock gains/losses
Retail — Percentage off, markup calculations
Science — Percent error between experimental and theoretical values
Business — Revenue growth, year-over-year comparisons
Fitness — Track weight loss or strength gains over time

Common Mistakes to Avoid

❌ Using the new value instead of the old value in the denominator
❌ Forgetting that a 50% drop followed by a 50% gain does NOT return to the original value
❌ Confusing percentage points with percentage change (interest rate going from 3% to 5% = 2 percentage points, but a 66.7% increase)