What Is a Percentage?
A percentage is a way of expressing a number as a fraction of 100. It tells you how many parts out of every hundred. For example, 25 % means 25 parts out of 100.
Expressing Percentages
You can write a percentage in three equivalent ways:
- As a percent sign: 25 %
- As a decimal: 0.25
- As a fraction: 25/100 (which reduces to 1/4)
How to Calculate a Percentage
To find what percentage one quantity (the part) is of another (the whole), use this formula:
Percentage (%) = (Part ÷ Whole) × 100
Example:
If you have 1 apple out of 100 total apples,
Percentage = (1 ÷ 100) × 100 = 1 %
Converting Between Forms
-
Percent → Decimal: Divide by 100
- 75 % ⇒ 75 ÷ 100 = 0.75
- 100 % ⇒ 100 ÷ 100 = 1
-
Decimal → Percent: Multiply by 100
- 0.45 ⇒ 0.45 × 100 = 45 %
Everyday Applications
- Shopping: Sales tax and discounts (e.g., 20 % off).
- Finances: Interest rates on savings or loans.
- Health/Nutrition: Percent daily values on food labels.
- Data Analysis: Interpreting survey results or performance metrics.
Why Learn Percentages?
- Better Decision-Making: Compare prices, calculate tips, or adjust recipes.
- Financial Literacy: Understand interest rates, loan payments, and investment returns.
- Clear Communication: Express changes and proportions (e.g., “Our sales grew by 10 % this quarter”).
Mastering percentages gives you a powerful tool for everyday math and informed choices—whether you’re budgeting, shopping, or analyzing data.