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Percentage Calculator

Find a percentage of a number, calculate a percentage share or compare two values by their percentage change.

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A visual example

The return journey uses a different percentage

An increase from 80 to 100 and a decrease from 100 to 80 both change the value by 20. Their percentage bases differ.

  1. Start
    80
    End
    100

    From 80 to 100: +25%

    The increase of 20 is divided by the starting value, 80: 20 ÷ 80 × 100 = 25%.

  2. Start
    100
    End
    80

    From 100 to 80: −20%

    The decrease of 20 is now measured against 100: −20 ÷ 100 × 100 = −20%.

For percentage change, always use the original value as the denominator.

Illustrative example. Select the change mode for this comparison. A change from a starting value of zero has no defined percentage in this calculation.

How to use it

  1. Choose percentage of a value, percentage share or percentage change.
  2. Enter both values. The result updates automatically.

15% of 200 is 30. A change from 80 to 100 is 25%.

Details & limits

Finite inputs up to 1 trillion in magnitude. A percentage share or change cannot have a zero baseline.

How is percentage change calculated?

The formula is (new value − original value) ÷ original value × 100. The original value cannot be zero. Negative baselines retain their sign; interpret negative-value comparisons carefully.

Choose the calculation that matches your question

Use percentage of a value for questions such as 15% of 80. Percentage share divides a part by its total. Percentage change compares the new value with the original value, which is the baseline. Share and change calculations cannot use a zero denominator. The calculator works locally with your entered numbers; it does not fetch prices or rates.

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