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Percentage Change Calculator

Relative increase, decrease or year-over-year change.

What does Percentage Change mean?

Percentage change measures how much a value has increased or decreased relative to its original amount. It is one of the most commonly used metrics in everyday life — from tracking stock price movements and salary raises to comparing test scores and population change. Businesses frequently use year-over-year percentage change (YoY) to compare performance across the same period in consecutive years, and month-over-month change (MoM) to track shorter movements. A positive percentage means an increase; a negative percentage means a decrease.

How to calculate Percentage Change

The formula is: Percentage Change = ((New Value − Old Value) / |Old Value|) × 100.

For example, if a product's price goes from $80 to $100, the change is ((100 − 80) / 80) × 100 = 25% increase. If it drops from $100 to $80, the change is ((80 − 100) / 100) × 100 = −20% decrease.

Note that a 25% increase followed by a 20% decrease returns to the original value — percentage changes are not symmetric.

Year-over-year change

Year-over-year (YoY) change is the same calculation applied to the same period in two consecutive years: (this year − last year) ÷ last year × 100. Switch the calculator above to Year over year mode to label the two inputs last year’s value and this year’s value.

Worked example: a company books revenue of $1.2M in 2025 against $950K in 2024. The change is (1,200,000 − 950,000) ÷ 950,000 × 100 = 250,000 ÷ 950,000 × 100 = +26.3% YoY. A negative result works the same way: $950K in 2025 against $1.2M in 2024 is (950,000 − 1,200,000) ÷ 1,200,000 × 100 = −20.8% YoY.

Because YoY compares like with like — Q3 to Q3, December to December, full year to full year — it cancels out seasonality. Month-over-month (MoM) change compares consecutive months instead, so it reacts much faster but mixes real growth with seasonal swings: a retailer’s December-to-January drop is a calendar effect, not a decline in the business. In practice MoM is the operational signal and YoY is the trend.

When the two values are more than one year apart, the raw percentage change covers the whole span, so it is not a yearly rate. Set Years apart above and the calculator also reports the annualized (CAGR) rate: (this year ÷ earlier year)1/years − 1, expressed as a percentage. Growing from $950K to $1.2M over 3 years is +26.3% in total but only about +8.1% per year.

FAQ

Because the base value changes. Going from 100 to 125 is a 25% increase (base 100), but going from 125 back to 100 is only a 20% decrease (base 125). The denominator is different in each direction, which is why the percentages differ.

Percentage change is undefined when the old value is zero, because you would be dividing by zero. In such cases, you can only describe the change in absolute terms, not as a percentage.

Percentage change is the relative difference between two values. Percentage points describe the absolute difference between two percentages. For example, if an interest rate goes from 5% to 7%, that is a 2 percentage point increase but a 40% percentage change.

Yes. A percentage change greater than 100% means the value more than doubled. For example, going from 50 to 150 is a 200% increase. There is no upper limit to percentage increases, though decreases are capped at −100% (the value drops to zero).

Multiply the old value by (1 + percentage / 100). For example, a 30% increase on $200: 200 × 1.30 = $260. For a 15% decrease on $200: 200 × 0.85 = $170.

Use the same percentage change formula: ((Current Price − Buy Price) / Buy Price) × 100. For example, if you bought a stock at $50 and it is now $65, the change is ((65 − 50) / 50) × 100 = 30% gain. Enter your buy price as the old value and the current price as the new value above to calculate instantly.

Subtract last year's value from this year's value, divide by last year's value, and multiply by 100: (this year − last year) ÷ last year × 100. For example, revenue of $920,000 this year against $800,000 last year is (920,000 − 800,000) ÷ 800,000 × 100 = 15% YoY growth. Always compare the same period in each year — Q3 to Q3, or January to January — so seasonality does not distort the result. Switch the calculator to Year over year mode to label the two inputs last year and this year.

Year-over-year (YoY) compares a period with the same period twelve months earlier, so seasonal patterns cancel out and what is left is the underlying trend. Month-over-month (MoM) compares a month with the month immediately before it, so it reacts much faster but mixes real growth with seasonal effects — a retailer almost always falls from December to January without anything going wrong. Teams usually watch MoM for operational decisions and YoY for the trend. The arithmetic is identical; only the two periods you pick differ.

A percentage change between values several years apart describes the whole span, not one year, so do not divide it by the number of years. Annualize it instead: (later value ÷ earlier value) raised to the power of 1 ÷ years, minus 1, times 100. Growing from $950,000 to $1,200,000 over 3 years is a 26.3% total change but only about 8.1% per year. In Year over year mode, set Years apart above 1 and this annualized (CAGR) rate is shown alongside the total change.

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