Percentage Basics

Percentages describe parts of 100. They’re one of the most common ways to express proportions, changes, and comparisons. Whether you’re looking at discounts, statistics, or simple math problems, percentages make it easy to understand how one value relates to another.

What a percentage represents

A percentage is a fraction of 100. The word literally means “per hundred.” So 25% means 25 out of 100, and 80% means 80 out of 100. Percentages give a consistent scale for comparing values.

The basic percentage formula

A common way to calculate a percentage is:

Percentage = (part / whole) × 100

This formula converts a fraction or ratio into a percentage by scaling it to 100.

A simple example

If you scored 45 points out of 50 on a quiz, you can calculate the percentage like this:

(45 / 50) × 100 = 90%

That 90% represents how much of the total you achieved.

Percentage increase and decrease

Percentages are also used to describe changes. A percentage increase shows how much a value has grown, while a percentage decrease shows how much it has shrunk. The basic idea is comparing the change to the original value.

Common misconceptions

• “Percentages can be more than 100 only by mistake.” They can exceed 100% when the part is larger than the whole.
• “Percentages and fractions are unrelated.” Percentages are simply fractions expressed out of 100.
• “A bigger percentage always means a bigger amount.” The whole matters — 50% of a small number can be less than 10% of a large number.

Percentages make comparisons simple and intuitive. Once you understand how they relate to fractions and ratios, they become one of the easiest tools for describing proportions and changes.