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Percentage Increase Calculator

Find the percent increase or decrease between two numbers, or apply one to a value.

Change from 80 to 100
25%
That is an increase of 25%.
Difference (new − original)20

Worked examples

80 rises to 100
Going from 80 to 100 is a difference of 20, which is (100 − 80) / 80 × 100 = a 25% increase.
100 falls to 80
Going from 100 to 80 is a difference of −20, which is (80 − 100) / 100 × 100 = a 20% decrease.
Apply 15% to 200
200 increased by 15% adds 30, giving 230. Decreased by 15% it removes 30, giving 170.
50 grows to 75
From 50 to 75 the difference is 25, so (75 − 50) / 50 × 100 = a 50% increase.

How the percentage increase calculator works

A percentage increase (or decrease) describes how much a number has changed relative to where it started. It is not the raw difference between two values, it is that difference expressed as a share of the original. This calculator does it two ways: work out the percent change between two numbers you already have, or apply a percent increase or decrease to a starting value.

The percent change formula

To compare an old value with a new one, use a single formula:

  • Percent change = (new − original) / original × 100

Subtract the original from the new value to get the difference, divide by the original, then multiply by 100. Take a value that rises from 80 to 100. The difference is 100 − 80 = 20, and 20 / 80 = 0.25, so 0.25 × 100 = 25%. The value went up by 25 percent.

The original value is the base you divide by, which is why it matters which number you start from. Swapping them changes the answer.

Increase versus decrease, and the sign

The same formula covers both directions. When the new value is larger, the result is positive and you read it as an increase. When the new value is smaller, the result is negative and you read it as a decrease:

  • From 50 to 75: (75 − 50) / 50 × 100 = 50%, an increase of 50%.
  • From 100 to 80: (80 − 100) / 100 × 100 = −20%, a decrease of 20%.

Notice that 80 to 100 is a 25% increase, but 100 to 80 is a 20% decrease, even though the gap is 20 in both cases. The percentages differ because they are measured against different starting points (80 in the first case, 100 in the second).

Applying a percent change to a value

Sometimes you already know the percentage and want the result. To raise or lower a number by a percent, multiply by one plus or minus the rate:

  • Increase: result = start × (1 + percent / 100)
  • Decrease: result = start × (1 − percent / 100)

So 200 increased by 15% is 200 × 1.15 = 230, adding 30. The same 200 decreased by 15% is 200 × 0.85 = 170, removing 30. This is the mode to reach for when adding a markup or a raise, or taking off a discount.

The gotcha: a rise then an equal fall does not undo itself

A 25% increase followed by a 25% decrease does not bring you back to where you started, and this trips people up constantly. Start at 100, add 25% to reach 125, then take 25% off 125. That removes 31.25 (a quarter of 125, not of 100), leaving 93.75. You end up below the original because the decrease is applied to the larger number.

The lesson: percentages only add and subtract cleanly when they share the same base. To reverse a 25% increase exactly, you need a decrease of 20% (125 × 0.8 = 100), not 25%.

Real uses

Percent change shows up everywhere: a price rising from $40 to $50 (a 25% increase), a salary bump, growth in monthly sales or website visits, changes in population, and the statistics quoted in the news. Keep percentage points and percent separate when reading those figures: a tax rate moving from 4% to 6% is a rise of 2 percentage points but a 50% increase. These results are for quick estimates and everyday math, so double check anything used for a financial or contractual decision.

Frequently asked questions

What is the percentage increase formula?
Percent change = (new value − original value) / original value × 100. Subtract the old value from the new one, divide by the old value, then multiply by 100. Going from 80 to 100 gives (100 − 80) / 80 × 100 = 25%, so it is a 25% increase.
What is the difference between a percent increase and a percent decrease?
It is simply the sign of the change. If the new value is larger than the original, the result is positive and you call it an increase. If the new value is smaller, the result is negative and you call it a decrease. The formula is the same either way: 100 to 120 is a 20% increase, and 120 to 100 is about a 16.7% decrease.
Why does a percent increase followed by an equal percent decrease not return to the start?
Because each percentage is taken from a different base. Raise 100 by 25% and you get 125. Now drop 125 by 25% and you remove 31.25 (25% of 125, not of 100), landing at 93.75. The increase was measured against 100 but the decrease was measured against the larger 125, so they do not cancel out.
What is the difference between percentage points and percent?
Percentage points measure the gap between two percentages, while percent measures relative change. If a rate goes from 4% to 6%, that is a rise of 2 percentage points, but a 50% increase (2 / 4 × 100). Mixing the two is a common source of misleading statistics.
What is a percentage increase calculator used for?
Common uses include price rises (a product going from $40 to $50 is a 25% increase), salary changes, growth in sales, website traffic or population, and reading statistics in the news. The apply mode is handy for adding a markup, a raise, or a discount to a starting figure.

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Last updated: 2026-07-02