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Percentage Calculator

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Your Results

15% of 200 is 30. To work it out, divide 15 by 100 to get 0.15, then multiply by 200. The other 85% of 200 is 170. Adding 15% to 200 gives 230.

30
15% of 200
230
200 Plus 15%
170
200 Minus 15%
0.15
Percent as a Decimal
3/20
Percent as a Fraction

What Is a Percentage?

A percentage is a number out of 100. "Per cent" means "for every hundred", so 15% means 15 out of every 100, which is the same as the fraction 15/100 or the decimal 0.15. Percentages make it easy to compare parts of different sizes: 30 out of 200 and 15 out of 100 are both 15%.

Which tab should I use?

  • % of Number: to find a part, such as 15% of 200. Use it for discounts, sales tax or commissions.
  • What %: to turn a part into a percent, such as a test score of 30 out of 200.
  • % Change: to see how much a number went up or down, such as a price going from 80 to 100.
  • Add / Subtract: to raise or lower a number by a percent, such as a price plus 15% or minus 20%.
  • For a tip on a restaurant bill, split between people, use the Tip Calculator.
  • To add sales tax to a price, take it out of a total or find the rate from a receipt, use the Sales Tax Calculator.

How to Calculate a Percentage

Each tab uses one short formula. To find a percent of a number:

Part=Percent100×Number

To find what percent one number is of another:

Percent=ValueTotal×100

To find the percent change from a starting value to a new one:

Change=New−Start|Start|×100

To add or subtract a percent:

Result=Start×(1±Percent100)
  • Percent: the percentage, such as 15 for 15%.
  • Number or Total: the whole amount the percent is taken from.
  • Value or Part: a piece of the total.
  • Start and New: the number before and after a change. The bars around Start mean its size without a minus sign.

Example

  • 15% of 200: 15 ÷ 100 × 200 = 30
  • 30 out of 200: 30 ÷ 200 × 100 = 15%
  • From 80 to 100: (100 − 80) ÷ 80 × 100 = 25%, an increase
  • 200 plus 15%: 200 × 1.15 = 230

Percent change is not the same both ways

Going from 80 to 100 is a 25% increase, but going back from 100 to 80 is a 20% decrease, because the change is measured against a different starting number. In the same way, adding 15% to 200 gives 230, but taking 15% off 230 gives 195.5, not 200. To get back, you take off 13.04%.

When neither number is the "before", such as two prices in different shops, people use the percentage difference instead: the gap divided by the average of the two numbers. For 80 and 100 it's 22.22%.

How to Use the Percentage Calculator

"What is 15% of 200?" This calculator answers that, and the other tabs answer the other common percent questions.

Let's enter the numbers for each example in the boxes. They are already filled in when the calculator opens, so you can follow along and then change any box. Each box takes whole numbers, decimals or negative numbers between -1 trillion and 1 trillion.

  • Percent (% of Number): Enter 15, which is the percentage you want.
  • Of Number (% of Number): Enter 200, which is the number you're taking the percent of.
  • Value (What %): Enter 30, which is the part, such as 30 correct answers.
  • Of Total (What %): Enter 200, which is the whole. It can't be 0.
  • Starting Value (% Change): Enter 80, which is the old number. It can't be 0, because a change from nothing has no percentage.
  • New Value (% Change): Enter 100, which is the new number.
  • Starting Value (Add / Subtract): Enter 200, which is the number to change.
  • Percent (Add / Subtract): Enter 15, which is how much to add or take off.
  • Add or Subtract: Choose Increase by the percent, or Decrease by the percent.

Calculate and Reset

Click Calculate to see your results. If a box has a problem, such as letters, an empty box or a total of 0, a message pops up under that box instead. With the default numbers you get:

  • Your Results: the answer in words, with the working, such as "divide 15 by 100 to get 0.15, then multiply by 200".
  • % of Number: the headline 30, with 200 plus 15% (230), 200 minus 15% (170), and 15% as a decimal (0.15) and a fraction (3/20).
  • What %: the headline 15%, with the decimal (0.15), the fraction (3/20), the rest of the total (170, or 85%) and 200 as a percent of 30 (666.67%).
  • % Change: the headline +25%, with the difference (+20), the percentage difference (22.22%), how many times bigger the new value is (1.25×) and the change that takes 100 back to 80 (-20%).
  • Add / Subtract: the headline 230, with the amount added (30), the multiplier (1.15×), the result as a percent of 200 (115%) and the percent change that takes you back to 200 (-13.04%).
  • Share Results: a link that opens this calculator on the same tab with your numbers filled in. Copy it, or share it on Facebook or X.

Click Reset to put the boxes on the tab you're using back to their defaults. Results show up to six decimal places.