Percentage Calculator

Runs entirely in your browser

Calculate a percentage of a number, find what percent one number is of another, or work out a percentage increase or decrease. Everything is calculated directly in your browser.

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How to use Percentage Calculator

  1. Choose the type of percentage calculation you need — "% of a number", "X is what % of Y" or "% increase/decrease".
  2. Enter the values for that calculation.
  3. Your result and a plain-language summary update instantly.

Features

  • Calculate a percentage of any number.
  • Find what percent one number is of another.
  • Work out percentage increase or decrease between two values.
  • Plain-language summary of every result.
  • 100% client-side — your figures are never sent to a server.

Worked Example

% of a number:        15% of 340        = 51
X is what % of Y:     45 is what % of 180 = 25%
% increase/decrease:  From 250 to 275     = 10% increase (difference: 25)

The third example uses ((To − From) / From) × 100 = ((275 − 250) / 250) × 100 = 10. If "To" were smaller than "From," the same formula would return a negative number, which the tool reports as a percentage decrease instead.

Things to know

  • Each of the three modes uses a different formula — mixing them up (for example, using "% increase/decrease" when you actually want "X is what % of Y") will give a technically correct but meaningless answer for your question.
  • "X is what % of Y" and percentage change both divide by one of your input values, so a zero in that position is mathematically undefined and shows an error rather than a result.
  • Percentage change is calculated relative to the "From" value, not the "To" value — a change from 200 to 100 is a 50% decrease, but a change from 100 to 200 is a 100% increase, even though the difference is the same 100 in both directions.

Is Percentage Calculator safe?

Yes. Whichever mode you pick — percentage of a number, ratio, or increase/decrease — the formula runs locally in your browser as you type, so the values you enter never leave your device.

Frequently Asked Questions

How do I calculate a percentage of a number?

Choose "% of a number", enter the percentage and the number. The result is the percentage multiplied by the number, divided by 100 — for example, 20% of 500 is 100.

How do I find what percent one number is of another?

Choose "X is what % of Y", enter the two values. The calculator divides the first value by the second and multiplies by 100 — for example, 25 is 20% of 125.

How is percentage increase or decrease calculated?

Choose "% increase/decrease", enter the original ("From") and new ("To") values. The calculator works out ((To − From) / From) × 100 — a positive result is an increase, a negative result is a decrease.

Why do I get an error when the base value is zero?

Percentage calculations that divide by a value — "X is what % of Y" and percentage change — are undefined when that value is zero, since dividing by zero has no meaningful percentage result.

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