Percentage calculator
Calculator finds solutions to common percentage problems. It's done in easy way: more like stories and everyday situations, less like math language.

1. Basics:

% is equal to
1.2. The number
is equal to
1.3. The fraction
is equal to
% from the number

2. Shopping:

2.1. The bike was at a price of
$. Next, its price has been raised by
%. After that, the bike costs
525 $
2.2. I'm a regular customer in The Shop and I obtained
% discount for future shopping. Regular price of washing machine is
$, but I will pay only
800 $
2.3. Yeah! There is a promotion this week - it's
% discount for all products. Some nice handbag costs
$ now. It means, the same handbag was at a price of
58.82 $ (58 $ and 82 cents)
2.4. The mobile phone costs
$ in first shop and
$ in another one. It means that, price offered by second shop is
20% higher

3. Bills:

3.1. My usual electricity bill is about
$ per month. Unfortunately, the bald man in TV was talking about upcoming increase of electricity price by
%. It means I will pay
151.5 $ (151 $ and 50 cents)
each month which is
1.5 $ (1 $ and 50 cents)
3.2. The landlord increased my rent by
$. Before that, I was paying
$ to him. This means my rent has grown by
3.3. My monthly gas bill is
$ in average. It turned out, that I would pay
$ when I switch to another supplier. It will be
20% less

Some facts#

  • One percent (1%) is equal to fraction 1/100 or 0,01:
    1 percent=1%=1100=0,011\ percent = 1\% = \dfrac{1}{100} = 0,01
  • To convert some number into percent, you need to convert it to fraction with 100 denominator first. Then, nominator of fraction will tell you "number of percents".
    ⓘ Example: Fraction 3/4 is equal to 75%, because after converting it to denominator 100 we get:
    34=3×254×25=75100=75%\dfrac{3}{4} = \dfrac{3 \times 25}{4 \times 25} = \dfrac{75}{100} = 75\%
  • If you need to calculate a percent of a number, you have to multiply that number by a proper fraction with 100 denominator.
    ⓘ Example: 50% from number 10 is equal to 5, because:
    50%×10=50100×10=50×10100=500100=550\% \times 10 = \dfrac{50}{100} \times 10 = \dfrac{50 \times 10}{100} = \dfrac{5\cancel{00}}{1\cancel{00}} = 5
  • The concept of percentage is very useful and popular in many areas of our life, for example:
    • Income from bank deposit is usually defined as percent of capital, that you would earn after one year. It's so called annual rate of return.
    • Change in a value is often expressed as percentage of inital value. For example: the handbag is 20% cheaper than it was before the summer discount.
    • Concentration of one substance in another is often expressed in percentage values (percentage concentration). For example you can buy 3% solution of hydrogen peroxide (H2O2) to desinfect wounds. It means that in 100g of solution you'll get 3g of the active substance (i.e. hydrogen peroxide).

Tips & tricks#

  • Use percentage commutativity and surprise your friends!
    • ⓘ Example: Let's calculate 18% from 50 in memory. Looks difficult? Don't worry - there is nothing easier. Let's swap number and percentage and we get 50% from 18. 50% of something is same as half of something ! So, we need half of 18, which is 9.
      18%×50=50%×18%=12×18=918\% \times 50 = 50\% \times 18\% = \dfrac{1}{2} \times 18 = 9
    • Why does it work? Percentage commutativity is related to multiplication commutativity. Because calculating percentage from given number is the same as multiplying this number by fraction (x/100), this operation is commutative too.
    • ⓘ Hint: Remember and impress friends: X% from number Y is the same as Y% from number X.
      X%×Y=Y%×XX\% \times Y = Y\% \times X

How to use this tool#

  • First of all, find the sentence in calculator, which describes your problem in the closest way. However, don't take those sentences too literally ! Those sentences describe example situations - like buying handbag under promotion. However, you can enter any other product in this place. Be creative, don't waste your imagination.
  • Next, click on one of input fields in the sentence and enter your own value.
  • After you've entered the numbers in the particular sentence, the other part of a sentence will adjust automatically, displaying the correct number as a solution.
  • Remember - if you can't find a sentence describing your situation, feel free to drop us a word. We will be happy to add the missing case for you!

Tags and links to this website#

What tags this calculator has#


Links to external sites (leaving Calculla?)#

Ancient version of this site - links#

In December 2016 the Calculla website has been republished using new technologies and all calculators have been rewritten. Old version of the Calculla is still available through this link: We left the version 1 of Calculla untouched for archival purposes.
Direct link to the old version:
"Calculla v1" version of this calculator
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