Percentage Change Calculator
Calculate the percentage increase or decrease between two values
Calculate Percentage Change
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How to Calculate Percentage Change
Percentage change measures how much a value has increased or decreased relative to its original value. The formula is: Percentage Change = ((New Value - Old Value) ÷ Old Value) × 100. A positive result means an increase; a negative result means a decrease.
Examples
If a stock price goes from $80 to $100, the percentage change is ((100-80) ÷ 80) × 100 = 25% increase. If your rent goes from $1,500 to $1,350, the change is ((1350-1500) ÷ 1500) × 100 = -10%, meaning a 10% decrease.
When to Use Percentage Change vs. Percentage Difference
Percentage change and percentage difference answer different questions and are calculated differently. Using the wrong one is a common error in business and academic contexts.
Percentage change measures how much a value has increased or decreased from an original (baseline) value. Use it when you have a clear starting point and ending point: "Sales grew from $100K to $130K — that's a 30% increase." Formula: ((New - Old) / Old) × 100.
Percentage difference measures how two values compare to each other without implying that one is the starting point. Use it when comparing two independent values: "City A's population is 50,000 and City B's is 65,000 — the percentage difference is 26%." Formula: (|A - B| / ((A + B) / 2)) × 100.
Common mistakes: A price dropping from $100 to $80 is a 20% decrease. But a price rising from $80 to $100 is a 25% increase — not 20%. This asymmetry trips up many people. The percentage depends on which number is the base. Going down 50% and then up 50% doesn't get you back to where you started — it leaves you at 75% of the original.
Calculating Percentage Change Accurately
Percentage change measures how much a value has grown or shrunk relative to its starting point. The formula is straightforward: subtract the old value from the new value, divide by the old value, and multiply by 100. A positive result indicates growth, while a negative result indicates decline. This calculation appears throughout finance (investment returns, revenue growth), economics (inflation rates, GDP changes), science (population changes, experimental results), and personal life (salary increases, weight changes).
A common pitfall is confusing percentage point changes with percentage changes. If an interest rate moves from 4% to 5%, that is a one percentage point increase but a 25% percentage change (because 1 divided by 4 equals 0.25). This distinction matters enormously in financial reporting and economic analysis. Our calculator provides both the percentage change and the absolute change, helping you communicate results accurately whether you are preparing a business report, analyzing scientific data, or simply tracking personal financial goals over time.