Percentages and basic math

Percentage calculator

Calculate percentages, percentage change, increases and decreases with a clear result and formula.

Calculate percentages

Example: 20% of 100 = 20.

What the percentage calculator does

The calculator covers five common percentage tasks: a percentage of a number, one number as a percentage of another, percentage change, increasing by a percentage and decreasing by a percentage.

Formulas

  • Percentage of a number = percentage / 100 x number.
  • Part as percentage of whole = part / whole x 100.
  • Percentage change = (new value - old value) / old value x 100.
  • Increase by percentage = value x (1 + percentage / 100).
  • Decrease by percentage = value x (1 - percentage / 100).

Examples

20% of 100 is 20. An increase from 100 to 125 is a 25% increase. Reducing 80 by 10% gives 72. The calculator also shows the formula behind the result so the calculation is easier to check.

How to choose the calculation type

Use the first mode when you know the percentage and the base number. Use percentage change when you compare an old value with a new value, and use increase or decrease modes when the percentage is applied to one value.

Common mistakes

Be careful with the base value. For example, 20% of 50 and 20 percentage points are different ideas. The formula shown with the result helps confirm which interpretation was used.

Percent and percentage points

A percent describes a relative share out of one hundred. A percentage point describes the difference between two percentages. Moving from 3% to 4% is one percentage point, but the relative increase is about 33.33%.

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