Percentage Calculator

Three calculators in one place, for the three ways people usually ask a percentage question. Type your numbers and the answer updates straight away, with the sum written out under it so you can check you filled the right boxes.

Find a percentage of a number

What is % of ?

3015% of 200

Work out what percentage one number is of another

is what percent of ?

25%45 out of 180

Percentage increase or decrease

From to

25% increasea rise of 20

Answers update as you type and round to two decimal places.

How to use the percentage calculator

  1. Pick the calculator that matches your question.
  2. Type your two numbers into the boxes.
  3. Read the answer in the highlighted box. It updates with every number you type.
  4. Answers are rounded to two decimal places.

The three calculators

  • What is X% of Y. For example, a 15% tip on a $200 bill is $30.
  • X is what percent of Y. For example, 45 correct answers out of 180 questions is 25%.
  • Percentage change from X to Y. For example, a price that goes from $80 to $100 has gone up by 25%.

The formulas behind each answer

Percent of a number: multiply the number by the percentage, then divide by 100. So 15% of 200 is 200 × 15 ÷ 100 = 30.

What percent one number is of another: divide the part by the whole, then multiply by 100. So 45 ÷ 180 × 100 = 25%.

Percentage change: take the new number away from the old one, divide by the old number, then multiply by 100. So (100 − 80) ÷ 80 × 100 = 25%.

Frequently asked questions

Why is going up 25% and then down 25% not the same?

Because each change is worked out from a different starting number. $80 up 25% is $100, but $100 down 25% is $75, not $80.

Can I use decimals and negative numbers?

Yes. All three calculators accept decimals and negative numbers.

Why does it say “Not possible”?

You cannot divide by zero, so a starting value or whole of zero has no percentage answer. Change that box to a number other than zero.

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