The Lesson

A percentage is a part of a whole. It expresses a part of a whole number as parts out of 100. A percentage is shown by the symbol % (said as "percent").

Dictionary Definition

The Merriam-Webster dictionary defines a percentage as "a part of a whole expressed in hundredths."

A Real Example of a Percentage

A percentage is written as a number followed by the percentage symbol %:

This is 20% (said as "20 percent"). It means 20 parts out of 100.

A Real Example of What a Percentage Means

Imagine you were given 20% in a mathematics exam. You would have got 20 out of every 100 marks.
  • If there were 100 marks, you would have got 20 marks.
  • If there were 200 marks, you would have got 40 marks.
  • If there were 50 marks, you would have got 10 marks.

Visualizing Percentages

A percentage shows how many parts out of a 100. A grid with 100 squares is a useful way of visualizing percentages. In the grid below, 20 out of 100 squares are colored blue. 20% of the squares are blue.

Lesson Slides

The slider below shows some more examples of visualizing percentages using a grid of 100 squares.

What's in a Name?

"Per cent" comes from the Latin "per centum", meaning "by the hundred". The word "cent" appears in many contexts. In currencies, a hundredth of a US dollar is a cent. A hundredth of a Euro is also a cent. A hundred years is called a century and a hundred year anniversary is a centennial.

Other Types of Fractional Numbers

Percentages express a part of a whole. There are other ways of expressing parts of a whole: For example:
  • A fraction: 1/2
  • A decimal: 0.5
  • A negative exponent: 2−1
  • A percentage: 50%
  • A ratio: 1:2