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Math

Percentage calculator

What X% of a number is, plus the value increased and decreased by that percentage.

Mathematics

Result

Fill in the fields and the result appears as you type.

B

Type the values into the fields and leave the rest to me.

How to use

The percentage calculator answers three questions at once: what X% of a number is, what that number becomes with X% added and what it becomes with X% removed. The same arithmetic covers a pay rise, a price increase, a commission and a tax.

  • Work out a commission, a fee or a share of an amount.
  • Apply an increase or a reduction and check the resulting figure.
  • Verify a discount or a surcharge quoted to you.
  1. Enter the base value.
  2. Enter the percentage.
  3. Read the standalone percentage, the value with the increase and the value with the decrease.

Formula

Part = value × (p ÷ 100) · Increased = value × (1 + p/100) · Decreased = value × (1 − p/100)

Example

15% of 200 is 30; increased, the value becomes 230, and decreased it becomes 170.

Limitations

  • A negative percentage flips direction: an increase of −10% is a 10% discount.
  • Successive percentages do not add up, because each one applies to the already changed value.

Frequently asked questions

How do I do percentages in my head?

10% is the value divided by 10, 5% is half of that and 1% is the value divided by 100. Combine the parts to reach 15%, 25% and so on.

Does a 50% rise followed by a 50% fall return to the start?

No. 100 rises to 150, and a 50% fall from 150 leaves 75.

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