A percentage is a way of expressing a part of a whole as a fraction of 100. It is one of the most widely used concepts in mathematics and daily life. For example, 50% means 50 out of 100, or simply half. Percentages are applied in grades, discounts, interest rates, taxes, profit and loss, population growth, and statistics.
This guide explains the different methods for calculating percentages, with clear examples and formulas that students and professionals can use daily.
Method 1: How to Find the Percentage of a Number
This is the most common percentage calculation students ask about. For example, what is 25% of 80 or 15% of 300?
The formula is:
Percentage of a number = (percentage ÷ 100) × number
Example 1:
25% of 80 = (25 ÷ 100) × 80
= 0.25 × 80
= 20
Example 2:
15% of 300 = (15 ÷ 100) × 300
= 0.15 × 300
= 45
Tip: On a calculator, convert the percentage to a decimal and multiply by the number. For instance, type 0.25 × 80 to get 20.

Method 2: How to Find the Percentage of a Part and a Whole
This method answers questions like “What percentage of 120 is 36?” or “What percentage of 50 is 10?”
The formula is:
Percentage = (part ÷ whole) × 100
Example 1:
Percentage = (36 ÷ 120) × 100
= 0.3 × 100
= 30%
Example 2:
Percentage = (10 ÷ 50) × 100
= 0.2 × 100
= 20%
Tip: On a calculator, divide the part by the whole, then multiply by 100.

Method 3: How to Calculate Percentage Change
Percentage change is useful in finding increases, decreases, profit, loss, or growth rates.
The formula is:
Percentage Change = ((new value – old value) ÷ old value) × 100
Example 1: Increase
From 80 to 100:
((100 – 80) ÷ 80) × 100
= (20 ÷ 80) × 100
= 0.25 × 100
= 25% increase
Example 2: Decrease
From 50 to 40:
((40 – 50) ÷ 50) × 100
= (-10 ÷ 50) × 100
= -0.2 × 100
= -20% decrease
Tip: Use a calculator by entering (new – old) ÷ old × 100 to get the change quickly.

Why Learning Percentages is Important
Percentages are not just classroom concepts. They are applied in:
- Exams and grades – understanding your score as a percentage.
- Shopping – calculating discounts and sales prices.
- Finance – interest rates, profit, and tax calculations.
- Statistics – interpreting surveys and data.
Mastering percentages builds confidence in solving math problems and helps in real-world decision-making.

Conclusion
This post explained three main methods of calculating percentages:
- Finding the percentage of a number.
- Finding the percentage of a part and a whole.
- Calculating percentage change.
With these formulas and examples, you can calculate percentages easily and accurately. Regular practice will help you solve percentage problems faster in exams and daily life.