To calculate a percentage, multiply the two numbers together and divide the result by 100, using the following formula: A x B / 100. For example, if we want to know how much is 30% of 150, just multiply 30 x 150 and then divide the result by 100. Then, we will have 4500 (return of 30 x 150) / 100 = 45. The concept is simple: take 30 units of a number divided into 100 parts; practically, we consider 1 hundredth of 150 which is equivalent to 1.5 and we calculate the desired percentage (in this case, 30) making a multiplication. Thus we will have 1.5 x 30 = 45. The same result is get using the proportion "A: C = B: 100", where A represents the unknown number that we want to know, C is the total and B is the number that quantifies the percentage (100). The relationship between the two numbers will be A: 150 = 30: 100. Since in the proportions the product of the means (30 and 150) is equal to the product of the extremes (A and 100), to know the unknown number A we will have to multiply 30 x 150 and divide the result by 100, obtaining 4500 : 100 = 45. Another explanation of the concept consists in transforming the percentage into a fraction (30% = 30/100, where 30 is the numerator and 100 is the denominator) to multiply by the number which represents the total (0.3 x 150).
In this page, the first calculator (the most used) has been joined by another 9, each of which shows the formula used and the explanation of the result, using the Direct Calculation and the Calculation of Inverse Percentage.
Attention: for decimals use the dot and not the comma (,).

Operations with Fractions
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Percentage Calculators

Percentage of an Amount

What is    % of  
decimals for rounding    
Formula: % amount = A x B / 100

The percentage calculation is used to determine a value multiplied by another divided into hundredths. The percentage can be quantified with a number followed by the symbol "%" (e.g. 50%), with a decimal number (0.5), or with a fraction (1/2).

Ratio between two numbers

The number:
is what percent of:
decimals for rounding    
Formula: % ratio = A / B x 100

The Percentage Ratio between two numbers, also called Incidence Rate, is used to determine the amount of one value compared to another. The operation is part of the "Inverse Percentages" and can be used, for example, to calculate the salary amount due for the payment of taxes.

Percent Change

Increase / decrease from:
compared to the number:
decimals for rounding    
Formula: % change = A - B / A x 100

The Percentage Change determines the amount of a value when it is compared with another. The result may show an increase or a decrease expressed as a percentage.

Get Total from Percentage

equals to % of no.
decimals for rounding    
Formula: total value = A / B x 100

This calculator allows you to go back to the total number starting from the percentage value of a number. For example, it's useful when you want to get the total number of voters knowing the absolute number and the relative percentage of votes attributed to a party.

Percentage Increment

Increase the below number
of the following percentage
%
decimals for rounding    
Formula: % increase = A + (A x B / 100)

The Percentage Increment indicates the amount of a value after a percentage increase is applied to it.

Percentage Decrease

Decrease the below number
of the following percentage
%
decimals for rounding    
Formula: % decrease = A - (A x B / 100)

The Percentage Decrease indicates the amount of a value after a percentage decrement is applied to it.

Initial value from increased number

Final number got
with percentage increase
%
decimals for rounding    
Formula: initial value = A / [ 1 + (B / 100) ]

This calculator is useful to determine the starting value when you know the final value (increased) and the percentage increase applied to the same starting value.

Initial value from decreased number

Final number got
with percentage decrease
%
decimals for rounding    
Formula: initial value = A / [ 1 - (B / 100) ]

This calculator is useful to determine the starting value when you know the final value (decreased) and the percentage decrease applied to the same starting value.

Percentage of a Percentage

What is the   % of   %
decimals for rounding     %
Formula: % of % = [ (A / 100) x (B / 100) ] x 100

Sometimes it happens to have to calculate the quota of a percentage and not its entire amount: a seller gives only a part of the discount set for an object, or you want to know the portion of a portion of the total. This calculator determines the percentage to be applied to the total.

Percentage Difference Calculator

% difference between 1st value
and 2nd value
decimals for rounding    
Formula: percentage difference = [ (a - b) / ((a + b) / 2) ] x 100

The Percentage Difference should not be confused either with the Incidence (or Ratio), or with the Percentage Change. To get it, is used a specific formula which calculates the difference between two values divided by their average. The Percentage Difference is used mainly in statistics when both values are homogeneous: for example, the population of two countries.

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