Percentage calculator

Percentages of numbers, percentage change and percentage difference, exactly.

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Percentage of a number

Percentage

Of number

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Value

Of total

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From

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First value

Second value

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All four calculations use exact decimal arithmetic, so results such as 10% of 0.3 come out as exactly 0.03, without floating-point errors.

Percentage change is (new − old) ÷ |old| × 100. Dividing by the size of the old value keeps the direction right for negative numbers: going from −50 to −25 is a 50% increase. Change from 0 is undefined.
Percentage difference is the gap between two values relative to their average. It does not depend on the order of the values and is only meaningful when both have the same sign.
Exact or rounded: results are shown exactly when they have up to 20 decimal places. Repeating decimals such as 1 ÷ 3 are rounded to 10 decimal places and marked with ≈.
Input: use a full stop for decimals and, optionally, commas between thousands (1,250.5). Up to 15 significant digits are accepted. Use the ± button to enter a negative number on keyboards without a minus key.