Calculate Percentage Change
This free percentage change calculator finds the percent increase or decrease between an old value and a new value. Enter the two numbers above and it instantly tells you how much they changed in percentage terms, and whether that change was an increase or a decrease. It is the fast, error-proof way to compare prices, scores, populations, or any two figures.
How to Use the Calculator
- Enter the old (original) value.
- Enter the new (current) value.
- Press Calculate to see the percentage change and whether it is an increase or decrease.
The Percentage Change Formula
Percentage change is found by subtracting the old value from the new value, dividing by the old value, and multiplying by 100: % change = ((new − old) ÷ old) × 100. A positive result is an increase; a negative result is a decrease. For example, going from 80 to 100 is ((100 − 80) ÷ 80) × 100 = 25% increase, while going from 100 to 80 is a 20% decrease — note the percentages differ because the starting point differs.
Worked Examples
A price that rises from $50 to $60 is a 20% increase. A stock that falls from $200 to $150 is a 25% decrease. A test score improving from 70 to 84 is a 20% increase. The calculator handles decimals and negative values, so it works for temperatures, profits, and any measurement that can go up or down.
Why the Starting Value Matters
A common source of confusion is that a percentage increase and the matching decrease are not the same size. If a $100 item rises 50% to $150, it then needs only a 33.3% decrease to return to $100 — because the decrease is calculated from the larger $150 base. This is why percentage change always divides by the original value, and why the calculator asks specifically for the old value first. Getting the base right is the key to an accurate result.
Where Percentage Change Is Used
Percentage change is everywhere in business and daily life. Retailers express price rises and markdowns as percentages; investors track gains and losses; analysts report growth in sales, traffic, or population; and scientists describe how a measurement changed between two readings. Because raw differences can be misleading — a $10 rise means something different on a $20 item than on a $1,000 one — percentage change puts every comparison on the same scale.
Percentage Change vs. Percentage Points
One important distinction: percentage change is not the same as percentage points. If an interest rate goes from 4% to 6%, that is a rise of 2 percentage points, but a 50% percentage change (because 2 is half of the original 4). Mixing these up is a frequent error in news and reports. This calculator gives the percentage change — the relative change from the old value — which is what most “percent increase” and “percent decrease” questions are really asking.
Frequently Asked Questions
How do I calculate percentage change?
Subtract the old value from the new value, divide by the old value, and multiply by 100. The tool above does it instantly.
Why isn’t a 50% increase cancelled by a 50% decrease?
Because the decrease is calculated from the larger new value. A 50% rise then a 50% fall leaves you below where you started.
Is the percentage change calculator free?
Yes — free, browser-based, and no signup needed.
Reading Percentage Change in the Real World
Percentage change is one of the most quoted numbers in news, finance, and business, so understanding it pays off. A headline that sales “rose 25%” tells you the relative size of the change regardless of the starting figure, which is why it is more meaningful than a raw dollar amount. Investors track percentage gains and losses to compare very different holdings on equal footing; a $5 move means something different for a $20 stock (25%) than for a $500 one (1%). Retailers, marketers, and analysts all lean on percentage change to report growth in traffic, revenue, prices, and audience size, which is exactly what this calculator produces from any two numbers.
Avoiding the Classic Mistakes
Two errors trip people up. First, a percentage increase and the equal-looking decrease are not symmetric: a value that rises 25% needs only a 20% fall to return to the start, because the base changed. Second, percentage change is not the same as a change in percentage points — a rate moving from 5% to 10% is a 5-point rise but a 100% change. Keeping the original value as the base, and being clear about whether you mean percent or percentage points, keeps your figures honest. The calculator always divides by the old value, so it gives the true relative change every time.
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