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Percentage Calculator

Four percentage questions in one place: what is X% of Y, X is what percent of Y, percentage change, and adding or removing a percentage.

Runs entirely in your browser

How to use the Percentage Calculator

  1. 1Pick the type of question you want to answer using the tabs.
  2. 2Type your numbers — the result updates as you type.
  3. 3Read the worked explanation below the answer to check the method.
  4. 4Switch tabs at any time; each keeps its own values.

How it works

A percentage is just a fraction with 100 on the bottom. Every calculation here is that one idea rearranged: to find a part you multiply, to find a rate you divide, and to find a change you compare the difference with where you started.

The one people most often get wrong is percentage change, because it matters which number you divide by. Going from 50 to 75 is a 50% increase, but going back from 75 to 50 is a 33.3% decrease — the same gap measured against a different starting point.

Results are rounded for display but calculated at full precision, so chaining answers together does not accumulate rounding error.

The formula

part = (percent ÷ 100) × whole percent = (part ÷ whole) × 100 change = ((new − old) ÷ old) × 100
percent
the rate, written without the % sign
whole
the number the percentage is taken from
part
the resulting amount
old / new
the values before and after the change

Percentage change always divides by the original value, which is why an increase and the decrease that undoes it are different percentages.

Worked example

A £80 jacket is reduced to £60

  1. Choose the percentage change tab.
  2. Enter 80 as the original value and 60 as the new value.
  3. The tool computes (60 − 80) ÷ 80 × 100.

Result: A 25% decrease — a saving of £20.

Frequently asked questions

How do I work out a percentage of a number?
Divide the percentage by 100 and multiply by the number. 15% of 240 is 0.15 × 240 = 36.
Why is a 50% rise not cancelled by a 50% fall?
Because each is measured against a different base. 100 rising by 50% gives 150; 150 falling by 50% gives 75, not 100. To undo a 50% rise you need a 33.3% fall.
What is the difference between percent and percentage points?
If a rate moves from 4% to 6% it has risen by 2 percentage points, but by 50 percent. Percentage points measure the gap between two rates; percent measures relative change.
How do I add tax or a tip to a price?
Use the "Add or subtract a percentage" tab. It multiplies by 1 plus the rate, so 20% added to 50 gives 60.

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