What is the difference between percentage change and percentage points?

Percentage change measures the relative change between two values as a proportion of the original value: ((New − Old) / |Old|) × 100. Percentage points measure the raw arithmetic difference between two percentages. If an approval rating moves from 40% to 50%, that is a 10 percentage point increase, but a 25% percentage change ((50−40)/40 × 100). The two describe the same event from different angles and are not interchangeable.

How do I calculate percent decrease?

Use the same formula as percentage change: ((New Value − Old Value) / |Old Value|) × 100. When the new value is smaller than the old value, the result is automatically negative, indicating a decrease. For example, a price dropping from $50 to $40 gives ((40−50)/50) × 100 = -20%, a 20% decrease.

What is the formula for percentage change?

The formula is Percentage Change = ((New Value − Old Value) / |Old Value|) × 100. New Value is the ending or current number, Old Value is the starting or original number, and the absolute value in the denominator ensures the result's sign correctly reflects an increase (positive) or decrease (negative).

Why do we divide by the old value and not the new value?

Percentage change measures how large the change is relative to where you started. Dividing by the old value answers "what fraction of the original amount did this change represent?" Dividing by the new value instead would answer a different question and produce a mathematically inconsistent result that doesn't match how percentage change is conventionally defined and reported.

Can percentage change be greater than 100%?

Yes. If a value more than doubles, the percentage change exceeds 100%. For example, going from 10 to 25 is a change of ((25−10)/10) × 100 = 150%. There is no upper limit on percentage increase, though percentage decrease cannot go below -100% (which represents the value dropping to zero).

How do you calculate percentage increase between two numbers?

Subtract the old number from the new number, divide the result by the old number, and multiply by 100. For example, going from 200 to 250: ((250−200)/200) × 100 = 25%, a 25% increase. If the result is negative, it represents a percentage decrease instead.

What does a negative percentage change mean?

A negative result means the new value is lower than the old value — in other words, the value decreased. A percentage change of -15% means the quantity dropped by 15% relative to its starting point, whether that's a falling stock price, a lower expense, or reduced body weight.

How is percentage change used to report inflation?

Government agencies such as the U.S. Bureau of Labor Statistics calculate inflation as the percentage change in the Consumer Price Index (CPI) between two time periods, typically year-over-year or month-over-month. A reported inflation rate of 3% means the average price level increased 3% compared to the prior period, calculated with the exact same percentage change formula used for any other comparison.

Percentage Change Calculator

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Calculate the percent increase or decrease between two values instantly

Old Value

New Value

A percentage change calculator answers one of the most common everyday math questions: how much did this number go up or down, expressed as a percentage? Prices rise, salaries get adjusted, stock values swing, and body weight fluctuates — and in every case, the raw dollar or pound difference tells only half the story. A $10 increase means very different things on a $20 item versus a $2,000 item. Percentage change puts every comparison on the same scale, so you can judge magnitude regardless of the starting number.

This tool takes your old value and new value and instantly calculates the percent increase or percent decrease between them, along with the direction of the change. Enter the price of a stock before and after a drop, your salary before and after a raise, or a product's cost before and after inflation, and get an accurate result in seconds — no manual division required.

Unlike a general percentage calculator that answers "what is X% of Y," this calculator is built specifically for comparing two values over time or across conditions, which is a distinct and very common calculation.

Why Percentage Change Calculator Matters

Percentage change is the standard way businesses, economists, and individuals communicate growth, decline, and comparison. Retailers advertise "20% off" by calculating the percent decrease from original to sale price. Government agencies like the Bureau of Labor Statistics report inflation as the percentage change in the Consumer Price Index from one period to the next — a 3.2% year-over-year CPI change means the average cost of goods rose 3.2%, not that prices rose by "3.2 dollars" or "3.2 points." Understanding this distinction is essential for interpreting news about the economy correctly.

In personal finance, percentage change tells you whether a raise actually kept pace with inflation, how much your investment portfolio grew or shrank in a given quarter, and how a stock's price move compares to its historical volatility. A $5,000 gain on a $10,000 stock position (50% increase) is a very different event than a $5,000 gain on a $500,000 position (1% increase), even though the dollar amount is identical. Investors and analysts rely on percentage change, not raw dollar figures, to compare performance across assets of different sizes.

The same logic applies to fitness and health tracking (a 10-pound weight loss means much more for someone starting at 150 pounds than someone starting at 300 pounds), and to business reporting, where KPIs like revenue, customer counts, and conversion rates are almost always presented as period-over-period percentage change so that leadership can quickly spot trends and rank priorities.

The Percentage Change Calculator Formula, Explained

Percentage Change = ((New Value − Old Value) / |Old Value|) × 100

Where: New Value = the value at the end of the period you're measuring (the current price, current salary, current weight), and Old Value = the value at the start of the period (the original price, previous salary, starting weight). The difference (New − Old) is divided by the absolute value of the Old Value, |Old Value|, rather than the Old Value itself. This matters when the old value is negative (for example, a company's net income moving from -$50,000 to $20,000) — dividing by the absolute value keeps the percentage change directionally correct and prevents the sign from flipping incorrectly.

The sign of the final result tells you the direction of the change: a positive percentage means the value increased, and a negative percentage means it decreased. A result of 25% is a 25% increase; a result of -25% is a 25% decrease. Some tools display the decrease as a positive number with a separate "decrease" label — this calculator shows the signed result so the direction is unambiguous at a glance.

How to Use the Percentage Change Calculator: Step by Step

Enter the old value
Input the starting number — the original price, previous salary, starting weight, or beginning measurement before the change occurred.
Enter the new value
Input the current or ending number — the value after the change you're measuring.
Calculate the difference
The calculator subtracts the old value from the new value to find the raw change, then divides by the absolute value of the old value.
Read the percentage result
Multiply by 100 to get the percentage change. A positive result is a percentage increase; a negative result is a percentage decrease.
Compare across scenarios
Use the signed percentage to compare changes of different sizes on equal footing — for example, comparing a raise at one job to a raise at another regardless of salary size.

Percentage Change Calculator Examples: Real-World Scenarios

Retail Price Increase

A grocery item that used to cost $80 now costs $92 due to inflation. What is the percentage increase?

Old value:$80

New value:$92

Calculation

((92 − 80) / |80|) × 100 = (12 / 80) × 100

Result

Percentage change: +15%. The item's price increased by 15%.

Annual Salary Raise

Maria's salary was $65,000 last year. After her annual review, it is now $71,500. What percentage raise did she receive?

Old value:$65,000

New value:$71,500

Calculation

((71500 − 65000) / |65000|) × 100 = (6500 / 65000) × 100

Result

Percentage change: +10%. Maria received a 10% raise.

Stock Price Decline

A stock was trading at $145 per share at the start of the month. It closed the month at $116 per share. What was the percentage change?

Old value:$145

New value:$116

Calculation

((116 − 145) / |145|) × 100 = (−29 / 145) × 100

Result

Percentage change: -20%. The stock lost 20% of its value over the month.

Common Mistakes to Avoid

Dividing by the new value instead of the old value — the denominator must always be the original (old) value, since percentage change measures the size of the change relative to where you started, not where you ended up.
Confusing percentage change with percentage points — if an interest rate moves from 5% to 7%, that is a 2 percentage point increase, but a 40% percentage change ((7−5)/5 × 100). These two figures describe the same event but are not interchangeable.
Forgetting or dropping the negative sign for a decrease — a drop from $100 to $80 is a -20% change, not a "20% change" with the direction implied; the sign carries meaningful information.
Not using the absolute value of the old value when it is negative — for example, when a business figure moves from a negative number (a loss) to a positive number (a profit), using the raw old value instead of its absolute value produces a mathematically incorrect and confusing sign.

Tips & Tricks

To quickly estimate percentage change in your head, round both numbers to the nearest convenient figure first, then adjust — an $80-to-$92 jump is close to a $80-to-$90 jump (about 12.5%), then adjust up slightly for the extra $2.
When comparing multiple percentage changes over time (like month-over-month sales), always chain them multiplicatively, not by adding the percentages — a 10% increase followed by a 10% decrease does not return you to the original value.
For inflation or cost-of-living comparisons, check whether the source is reporting percentage change or percentage points — government releases like CPI reports typically state the percentage change explicitly, but headlines sometimes blur the two.

Percentage change is a simple formula with an outsized role in how we interpret prices, pay, investments, and performance data. Getting the direction and magnitude right — and avoiding the classic mistake of dividing by the wrong value — makes the difference between a useful comparison and a misleading one. If you're working with two values you want to compare directly rather than as a change over time, try our general Percentage Calculator, or use the Compound Interest Calculator to see how repeated percentage changes compound over multiple periods.

Percentage Change Calculator — Frequently Asked Questions

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Authoritative References

Khan Academy — Percent Word Problems

khanacademy.org — Educational reference for percentage change concepts

Investopedia — Percentage Change Definition

investopedia.com — Financial definition and examples of percentage change

U.S. Bureau of Labor Statistics — Consumer Price Index

bls.gov — Official inflation data reported as percentage change

External links open in a new tab. OmniCalc.us is not affiliated with these organisations.

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