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.
Helpful context
Percentage change is one of the clearest ways to explain growth or decline because it relates the difference back to the original amount. Businesses use it for revenue and traffic reports, students use it for data tables, and everyday users rely on it for price comparisons. The key is identifying the original value correctly before calculating the increase or decrease.
Practical example
The Percentage Change Calculator page is also a good double-check when you are moving between calculator results and spreadsheet work. Many people know the rough idea of the math but still make small setup errors when a value needs to be rounded, reformatted, or interpreted in context. Keeping the explanation tied to the specific percentage change calculator workflow makes those mistakes easier to catch.
When reporting percentage change, it also helps to pair the rate with the raw numbers involved. Seeing both the absolute difference and the percentage tells a fuller story and prevents large-looking rates from being misunderstood when the original values were small.
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.