One percent (1%) means 1 per 100.

1% of this line is shaded green: it is very small isn't it?

 

| 50% means 50 per 100
(50% of this box is green)

25% means 25 per 100
(25% of this box is green) |

 

Examples:

|   | 100% means all.Example:100% of 80 is 100/100 × 80 = 80

|   | 50% means half.Example:50% of 80 is 50/100 × 80 = 40

|   | 5% means ⁵/_100ths.Example:5% of 80 is 5/100 × 80 = 4

"this should be divided by 100"

So 75% really means 75100

And 100% is 100/100, or exactly 1 (100% of any number is just the number, unchanged)

And 200% is 200/100, or exactly 2 (200% of any number is twice the number)

 

A Percent can also be expressed as a Decimal or a Fraction

|   | A Half can be written... | 
  | 
As a percentage: | 50%
As a decimal: | 0,5
As a fraction: | ¹/₂

Read more about this at Decimals, Fractions and Percentages.

Some Worked Examples

Example: Calculate 25% of 80

25% = 25/100

And  25/100 × 80 = 20

So 25% of 80 is 20

Example: 15% of 200 apples are bad. How many apples are bad?

15% = 15/100

And  15/100 × 200 |   | =  15 × 200100
  |   | =  15 × 2 
  |   | =  30 apples

30 apples are bad

Example: if only 10 of the 200 apples are bad, what percent is that?

As a fraction, 10/200 = 0,05

As a percentage it is: 10/200 x 100 = 5%

 

5% of those apples are bad

Example: A Skateboard is reduced 25% in price in a sale. 
The old price was $120. 
Find the new price.

 

First, find 25% of $120:

25% = 25/100

And  25/100 × $120 = $30

25% of $120 is $30

So the reduction is $30

 

Take the reduction from the original price

$120 − $30 = $90

The Price of the Skateboard in the sale is $90

| 

A Half can be written...
  | 
As a fraction: | ¹/₂
As a decimal: | 0,5
As a percentage: | 50%

| 

A Quarter can be written...
  | 
As a fraction: | ¹/₄
As a decimal: | 0,25
As a percentage: | 25%

Here, have a play with it yourself:

Twenty Seven One-Hundredths© 2015 MathsIsFun.com v 0,81 | 27% | 

Example Values

Here is a table of commonly used values shown in Percent, Decimal and Fraction form:

Percent Decimal Fraction
1% | 0,01 | ¹/₁₀₀
5% | 0,05 | ¹/₂₀
10% | 0,1 | ¹/₁₀
12½% | 0,125 | ¹/₈
20% | 0,2 | ¹/₅
25% | 0,25 | ¹/₄
33¹/₃% | 0,333... | ¹/₃
50% | 0,5 | ¹/₂
75% | 0,75 | ³/₄
80% | 0,8 | ⁴/₅
90% | 0,9 | ⁹/₁₀
99% | 0,99 | ⁹⁹/₁₀₀
100% | 1 | 
125% | 1,25 | ⁵/₄
150% | 1,5 | ³/₂
200% | 2 | 

To convert from percent to decimal: divide by 100, and remove the "%" sign.

The easiest way to divide by 100 is to move the decimal point 2 places to the left:

From Percent | To Decimal | 

| move the decimal point 2 places to the left, and remove the "%" sign.

 

From Decimal to Percent

To convert from decimal to percent: multiply by 100, and add a "%" sign.

The easiest way to multiply by 100 is to move the decimal point 2 places to the right:

From Decimal | To Percent | 

| move the decimal point 2 places to the right, and add the "%" sign.

 

From Fraction to Decimal

The easiest way to convert a fraction to a decimal is to divide the top number by the bottom number (divide the numerator by the denominator in mathematical language)

Example: Convert ²/₅ to a decimal

Divide 2 by 5: 2 ÷ 5 = 0,4

 

Example: To convert 0,75 to a fraction

StepsExample
First, write down the decimal "over" the number 1 | 0,75
1
  | 
Multiply top and bottom by 10 for every number after the decimal point (10 for 1 number, 100 for 2 numbers, etc) | 0,75 × 100
1 × 100
(This makes a correctly formed fraction) | 75
100
Then Simplify the fraction | 3
4

 

From Fraction to Percentage

The easiest way to convert a fraction to a percentage is to divide the top number by the bottom number. then multiply the result by 100, and add the "%" sign.

Example: Convert ³/₈ to a percentage

First divide 3 by 8: 3 ÷ 8 = 0,375,
Then multiply by 100: 0,375 x 100 = 37,5
Add the "%" sign: 37,5%

 

From Percentage to Fraction

To convert a percentage to a fraction, first convert to a decimal (divide by 100), then use the steps for converting decimal to fractions (like above).

Example: To convert 80% to a fraction

StepsExample
Convert 80% to a decimal (=80/100): | 0,8
  | 
Write down the decimal "over" the number 1 | 0,8/1
  | 
Multiply top and bottom by 10 for every number after the decimal point (10 for 1 number, 100 for 2 numbers, etc) | 0,8 × 10
1 × 10
(This makes a correctly formed fraction) | 8/10
Then Simplify the fraction | 4/5