Calculate percentage increase or decrease between two values. Perfect for analyzing price changes, salary adjustments, business growth, and more.
Original or initial value
New or ending value
Product price dropped from $50 to $40
Monthly salary increased from $3,000 to $3,300
Stock price fell from $100 to $85
Company revenue grew from $1M to $1.2M
In words: (New Value − Old Value) ÷ Old Value × 100%.
This formula is your go-to tool for comparing any two numbers in context. Whether you're tracking stock prices, analyzing sales data, or just comparing grocery prices from last month, percentage change gives you a standardized way to measure growth or decline.
Tesla Stock Drop
Price fell from $120 to $90
Calculation:
=
= -25% (25% decrease)
Annual Review Bonus
Monthly pay: $5,000 → $5,750
Calculation:
=
= 15% (pay raise!)
Laptop Sale
Price: $299 → $199
How good is this deal?
=
≈ -33.4% (1/3 off!)
📊 Percentage Change
Interest rate: 5% → 8%
(Relative to the original 5%)
📍 Percentage Points
Interest rate: 5% → 8%
8 - 5 = 3 percentage points
(Absolute difference)
Here's something that trips people up: if your stock goes up 50% then down 50%, you don't end up where you started!
Example: $100 investment
Result: You lost $25 (25% total loss)
💡 This is because percentage changes are multiplicative, not additive. The second percentage operates on an already-changed base value.
Track your portfolio performance, compare mutual funds, or calculate ROI on property investments. Essential for making data-driven financial decisions.
Month-over-month revenue growth, customer acquisition rates, conversion rate improvements. Every business dashboard uses percentage change.
Amazon price trackers, gas price trends, real estate market analysis. Know when you're getting a genuine deal vs. fake "discounts."
Feature engineering for machine learning models. Normalizing time-series data. Calculating model performance improvements.
Ever wonder how the government tracks inflation? The U.S. Bureau of Labor Statistics (BLS) uses exactly the same percentage change formula you see above — just applied to a basket of goods called the Consumer Price Index (CPI) .
Real BLS Calculation Example:
Say the CPI index was 304.127 in January 2025 and 309.685 in January 2026.
= ≈ 1.83% year-over-year inflation
This is exactly what financial news means when they say "inflation rose 1.83%." No fancy statistics — just the percentage change formula applied to price index data.
💡 Why this matters to you: When the Fed raises interest rates "because inflation is at 3.2%," they're reacting to a percentage change number. Your mortgage rate, rent increases, and cost-of-living adjustments at work all trace back to this single formula. Understanding it gives you a head start in making sense of economic headlines.
You don't always need a calculator. Here are shortcuts I use when eyeballing percentage changes:
🔟 The "Move the Decimal" Trick
10% of anything = move the decimal one place left. So 10% of $85 = $8.50. Then 20% = double that, 5% = half of 10%.
🔄 The "Doubling" Rule
If something doubled, that's always +100%. Tripled? +200%. Cut in half? -50%. These anchors help you sanity-check your calculations.
📐 The "Third" Shortcut
33% ≈ one-third. So a 33% discount on $90 is roughly $30 off. Works great for splitting checks at dinner too.