How to Calculate Percentage
A practical guide to calculating percentages, percentage change, increases and decreases.
Learning how to calculate percentage is useful for exam marks, discounts, salary changes, savings, business calculations and many everyday situations. A percentage expresses a value as a fraction of 100.
In this guide, you will learn the basic percentage formula and practical methods for calculating the percentage of a number, percentage of marks, percentage of money, percentage increases and decreases, and percentage change. We also cover how to calculate percentage in Excel and on a mobile phone.
What Is a Percentage?
A percentage is a way of expressing a value out of 100. The symbol used for percentage is %.
For example, 25% means 25 out of 100, which is the same as 0.25 or 1/4.
Basic percentage formula
Percentage = (Part ÷ Whole) × 100
How to Calculate a Percentage
To calculate what percentage one number represents of another, divide the part by the whole and multiply the result by 100.
Example: 25 out of 200
Suppose you want to know what percentage 25 is of 200:
Percentage = (25 ÷ 200) × 100
Percentage = 12.5%
Therefore, 25 is 12.5% of 200.
How to Find a Percentage of a Number
If you already know the percentage and want to calculate the corresponding amount, convert the percentage to a decimal and multiply it by the number.
Formula
Percentage Amount = (Percentage ÷ 100) × Number
Example: 20% of 500
20% of 500 = (20 ÷ 100) × 500
= 0.20 × 500
= 100
So, 20% of 500 is 100.
How to Calculate Percentage Increase
Percentage increase tells you how much a value has increased compared with its original value.
Percentage increase formula
Percentage Increase = ((New Value − Original Value) ÷ Original Value) × 100
Example: Increase from 200 to 250
Percentage Increase = ((250 − 200) ÷ 200) × 100
= (50 ÷ 200) × 100
= 25%
The value increased by 25%.
How to Calculate Percentage Decrease
Percentage decrease measures how much a value has fallen compared with its original value.
Percentage decrease formula
Percentage Decrease = ((Original Value − New Value) ÷ Original Value) × 100
Example: Decrease from 500 to 400
Percentage Decrease = ((500 − 400) ÷ 500) × 100
= (100 ÷ 500) × 100
= 20%
The value decreased by 20%.
How to Calculate Percentage Change
Percentage change is commonly used when comparing an old value with a new value. The standard formula uses the original value as the base.
Percentage change formula
Percentage Change = ((New Value − Original Value) ÷ Original Value) × 100
A positive result indicates an increase, while a negative result indicates a decrease.
Percentage Increase and Decrease Examples
| Original | New | Change |
|---|---|---|
| 100 | 120 | 20% increase |
| 200 | 150 | 25% decrease |
| 500 | 650 | 30% increase |
How to Calculate Percentage of Marks
To calculate the percentage of marks, divide the marks obtained by the total possible marks and multiply by 100.
Percentage of marks formula
Percentage = (Marks Obtained ÷ Total Marks) × 100
Example: Marks in 6 subjects
Suppose a Class 10 student scores 78, 82, 75, 88, 80 and 77 marks in six subjects, with each subject carrying 100 marks.
Total marks obtained = 78 + 82 + 75 + 88 + 80 + 77 = 480
Total marks = 6 × 100 = 600
Percentage = (480 ÷ 600) × 100
= 80%
Therefore, the student's percentage for 6 subjects is 80%. The same method can be used when each subject has a different maximum mark.
How to Calculate Percentage of Class 10
To calculate the Class 10 percentage, add the marks obtained in the subjects that are included in the calculation. Then divide the total obtained marks by the maximum total marks and multiply by 100.
Class 10 Percentage = (Total Marks Obtained ÷ Maximum Total Marks) × 100
For example, 450 marks out of 500 gives:
(450 ÷ 500) × 100 = 90%
When calculating an actual school-board result, use the subjects and maximum marks specified by the relevant board or result format.
How to Calculate Percentage of Money
The method for calculating a percentage of money is the same as for any other number. Convert the percentage to a decimal and multiply it by the amount.
Formula
Percentage of Money = (Percentage ÷ 100) × Amount
Example: 15% of ₹20,000
15% of ₹20,000 = (15 ÷ 100) × ₹20,000
= ₹3,000
So, 15% of ₹20,000 is ₹3,000. This method can be used for discounts, tax amounts, commissions and savings.
How to Calculate Percentage of a Number
To calculate a percentage of a number, divide the percentage by 100 and multiply the result by the number.
35% of 240 = (35 ÷ 100) × 240
= 84
Therefore, 35% of 240 is 84.
How to Calculate Percentage in Excel
Excel can calculate percentages using the same formulas used in manual calculations. If the part is in cell A2 and the whole is in cell B2, use:
=A2/B2
Format the result cell as Percentage to display the result with the % symbol. If A2 is 75 and B2 is 100, the result is 75%.
For percentage change from an original value in A2 to a new value in B2, use:
=(B2-A2)/A2
How to Calculate Percentage on a Mobile
You can calculate a percentage on a mobile phone using the calculator app. For example, to find 20% of 500:
500 × 20 ÷ 100 = 100
You can also use the Percentage Calculator on your mobile browser for percentage changes, increases and decreases.
How to Calculate a Discount Percentage
To calculate the percentage discount, first find the difference between the original price and the sale price. Then divide that difference by the original price and multiply by 100.
Discount percentage formula
Discount % = ((Original Price − Sale Price) ÷ Original Price) × 100
Example: ₹1,000 reduced to ₹800
Discount = ₹1,000 − ₹800 = ₹200
Discount % = (₹200 ÷ ₹1,000) × 100
= 20%
The discount is 20%.
How to Calculate a Percentage in Everyday Situations
Percentages can be useful for many common calculations:
- Calculating discounts during shopping
- Comparing exam or test scores
- Measuring increases or decreases in prices
- Understanding business growth
- Calculating tax as a percentage
- Comparing changes in savings or investments
Quick Percentage Shortcuts
Some percentages are especially easy to calculate mentally:
- 10% of a number = divide by 10.
- 5% of a number = half of 10%.
- 1% of a number = divide by 100.
- 50% of a number = half of the number.
- 25% of a number = one-quarter of the number.
Percentage vs Percentage Points
Percentage and percentage points are not always the same thing. For example, if a rate changes from 20% to 25%, the difference is 5 percentage points.
However, the relative increase is:
((25 − 20) ÷ 20) × 100 = 25%
So the rate increased by 5 percentage points, or 25% relative to its original value.
Use a Percentage Calculator
For quick calculations, you can use the Percentage Calculator to calculate percentages, percentage changes, increases and decreases without doing the calculation manually.