How to Calculate Percentage: Formulas, Examples & Tricks
You see percentages every day: a 30% discount on a shirt, 18% GST on a bill, 86% marks in an exam, or a phone battery at 15%. If you know how to calculate percentage quickly, you can check a bill, compare two deals and understand your results without depending on a calculator every time.
This guide explains the percentage formula step by step, with percentage examples in rupees and marks, and shows mental math tricks you can use in daily life. It is written for students, teachers, shoppers and anyone who wants to stop guessing with percentages.
- What is a percentage?
- The basic percentage formula
- Percentage of a number (with example)
- Find what percent one number is of another (example)
- Find the whole from a percentage (example)
- Percentage increase and decrease formula with example
- Percentage difference formula with example
- Discount percentage formula with example
- GST calculation formula with example
- Profit and loss percentage with example
- Percentage of marks example
- Percentage examples at a glance
- Percentage tricks without a calculator
- Common mistakes to avoid
- Practice questions
- FAQ
What Is a Percentage?
The word "percent" means "out of 100". So 45% means 45 out of 100, which can also be written as the fraction 45/100 or the decimal 0.45.
Percentages make comparison easy. Scoring 18 out of 20 in one test and 43 out of 50 in another is hard to compare directly. Converted into percentages, they become 90% and 86%, and the comparison is instant.
The Basic Percentage Formula
Every percentage problem has three values: the part, the whole and the percent. If you know any two, you can find the third.
| What you want | Formula | Example |
|---|---|---|
| The percent | (Part ÷ Whole) × 100 | 60 out of 240 = 25% |
| The part | (Percent ÷ 100) × Whole | 25% of 240 = 60 |
| The whole | Part ÷ (Percent ÷ 100) | 60 is 25% of 240 |
How to Find the Percentage of a Number (With Example)
This is the most common question: "What is X% of Y?"
Example 1: What is 25% of 240?
Example 2: 15% off on a ₹3,500 jacket
How to Find What Percent One Number Is of Another (Example)
Example: 18 marks out of 24 in a quiz
How to Find the Whole From a Percentage (Example)
Example: 60 students passed, which is 75% of the class
Percentage Increase and Decrease Formula With Example
Percentage increase formula
Use this when a value goes up, such as salary, price or followers.
Example: salary rises from ₹25,000 to ₹28,000
Percentage decrease formula
Example: phone price drops from ₹20,000 to ₹16,500
Percentage Difference Formula With Example
Use percentage difference when two values are equally important and neither is the "old" one, such as comparing the prices of two shops.
Example: Shop A sells an item for ₹40 and Shop B for ₹60
Discount Percentage Formula With Example
Example: ₹2,500 shoes at 40% off
To find the discount percentage when you know both prices: Discount % = ((Original − Sale) ÷ Original) × 100. If a ₹1,200 item sells for ₹900, the discount is (300 ÷ 1,200) × 100 = 25%.
Double discounts do not simply add up
A "30% off + extra 10% off" offer is calculated one after another: 0.70 × 0.90 = 0.63. You pay 63% of the price, so the total discount is 37%, not 40%. To check any sale quickly, use our Black Friday Discount Calculator.
GST Calculation Formula With Example
GST is a percentage added on top of the base price.
Example: adding 18% GST to ₹5,000
Final Price = Base Price × (1 + GST rate ÷ 100)
Example: removing 18% GST from ₹5,900
Base Price = Final Price ÷ (1 + GST rate ÷ 100)
You can check any amount with our GST Calculator for India. GST rates differ by product and change over time, so confirm the current rate on the official GST portal. This guide is for learning and is not tax advice.
Profit and Loss Percentage Formula With Example
Loss % = ((Cost Price − Selling Price) ÷ Cost Price) × 100
Example: bought for ₹400, sold for ₹480
Profit and loss are always calculated on the cost price.
How to Calculate Percentage of Marks (Example)
Percentage = (Marks Obtained ÷ Total Marks) × 100
Example: 78, 85, 92, 70 and 88 in five subjects (each out of 100)
If you have a CGPA instead, you can convert it using the CGPA tool in our percentage tools section. Always check the conversion rule your own board or university uses, because it can differ.
Percentage Examples at a Glance
Here are quick percentage examples from daily life, so you can see which formula fits which situation.
| Situation | Percentage example | Answer |
|---|---|---|
| Exam marks | 432 out of 500 | 86.4% |
| Shopping discount | ₹2,500 at 40% off | ₹1,500 |
| Salary hike | ₹25,000 to ₹28,000 | 12% increase |
| Price drop | ₹20,000 to ₹16,500 | 17.5% decrease |
| GST on a bill | ₹5,000 + 18% | ₹5,900 |
| Shop profit | Cost ₹400, sold ₹480 | 20% profit |
| Restaurant tip | 10% of ₹1,850 | ₹185 |
Percentage Tricks Without a Calculator
These shortcuts handle most everyday situations in your head.
| Percent | Shortcut | Example |
|---|---|---|
| 10% | Move the decimal one place left | 10% of 3,500 = 350 |
| 1% | Move the decimal two places left | 1% of 3,500 = 35 |
| 5% | Half of 10% | 5% of 3,500 = 175 |
| 15% | 10% + 5% | 15% of 80 = 8 + 4 = 12 |
| 20% | Divide by 5 | 20% of 450 = 90 |
| 25% | Divide by 4 | 25% of 240 = 60 |
| 50% | Divide by 2 | 50% of 86 = 43 |
| 12.5% | Divide by 8 | 12.5% of 640 = 80 |
The swap trick: X% of Y is always equal to Y% of X. So 4% of 75 is the same as 75% of 4, which is 3.
Fractions worth memorising: 1/2 = 50%, 1/4 = 25%, 3/4 = 75%, 1/5 = 20%, 1/8 = 12.5%, 1/3 ≈ 33.3%.
Want to get faster? Play our free percentage games for students and build speed with daily practice.
Common Percentage Mistakes to Avoid
- Misplacing the decimal. 5% is 0.05, not 0.5.
- Using the wrong base. A percentage is always "of" something. Decide what the 100% is before you calculate.
- Adding successive percentages. A 10% rise followed by another 10% rise is a 21% total rise (1.10 × 1.10 = 1.21).
- Assuming a fall and a rise cancel out. If a price falls 20% and then rises 20%, you end at 96, not 100 (100 80 96).
- Mixing percent and percentage points. If an interest rate moves from 10% to 12%, that is a rise of 2 percentage points but a 20% increase in the rate itself.
Practice Questions
Try these percentage examples yourself first, then open the answers.
- What is 18% of 650?
- 36 is what percent of 240?
- A price rises from ₹800 to ₹920. What is the percentage increase?
- After a 20% discount, a bag costs ₹1,200. What was the original price?
- A ₹4,000 item has 12% GST added. What is the final price?
Show answers
- 0.18 × 650 = 117
- (36 ÷ 240) × 100 = 15%
- (120 ÷ 800) × 100 = 15%
- 1,200 ÷ 0.80 = ₹1,500
- 4,000 × 1.12 = ₹4,480
For more practice, download our printable percentage worksheets with answer key. Hindi readers can also read Percentage Kaise Nikale (Hindi guide).
Frequently Asked Questions
How do I calculate percentage without a calculator?
Start with 10% by moving the decimal one place left, then build up from it. For example, 15% is 10% plus half of 10%, and 25% is simply one quarter of the number.
What is the formula for percentage?
Percentage = (Part ÷ Whole) × 100.
Can you give a simple percentage example?
Yes. To find 20% of 450, divide 20 by 100 to get 0.20, then multiply 0.20 × 450 = 90.
How do I find the percentage of a number?
Convert the percentage into a decimal by dividing it by 100, then multiply it by the number. For example, 18% of 650 is 0.18 × 650 = 117.
How do I calculate percentage increase between two numbers?
Subtract the old value from the new value, divide by the old value, and multiply by 100.
How do I convert a decimal to a percentage?
Multiply the decimal by 100. For example, 0.35 becomes 35%.
Can a percentage be more than 100?
Yes. If a value doubles, it has grown by 100%, and a value can be 150% of another number. In exams, however, marks cannot normally exceed 100%.
What is the difference between percent and percentage points?
Percentage points measure the plain gap between two percentages (10% to 12% is 2 points). Percent change measures the relative change (10% to 12% is a 20% increase).
Conclusion
Every percentage problem comes back to the same three pieces: the part, the whole and the percent. Once you know which one is missing, the formula is clear. Practise with real numbers from daily life, such as bills, discounts and marks, and these calculations will soon feel automatic. Bookmark this page as a quick reference, and try the Percentage Calculator Games to turn practice into a habit.
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