Comprehensive Guide

Percentage Formula: How to Calculate Percentages

Quick Answer: What Is the Percentage Formula?

The basic percentage formula is:

Percentage = (Part ÷ Whole) × 100

For example, if you scored 45 marks out of 60:

(45 ÷ 60) × 100 = 75%

So, your percentage is 75%.

The most important part of any percentage calculation is identifying the whole — the number that represents the total or original amount.

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Percentage Formula Cheat Sheet

What you want to calculate	Formula
Basic percentage	`(Part ÷ Whole) × 100`
Percentage of a number	`(Percentage ÷ 100) × Number`
Find the whole	`Part ÷ (Percentage ÷ 100)`
Percentage of marks	`(Marks obtained ÷ Total marks) × 100`
Percentage change	`((New − Old) ÷ Old) × 100`
Percentage increase	`(Increase ÷ Original) × 100`
Percentage decrease	`(Decrease ÷ Original) × 100`
Percentage difference	`\|A − B\| ÷ ((A + B) ÷ 2) × 100`
Discount percentage	`((Original − Sale) ÷ Original) × 100`
Profit percentage / markup	`(Profit ÷ Cost) × 100`
Profit margin	`(Profit ÷ Selling price) × 100`

What Is a Percentage?

The word percent means "per hundred." A percentage expresses a number as a portion of 100.

30% = 30 out of 100
50% = 50 out of 100
75% = 75 out of 100
100% = the entire amount

To convert a percentage into a decimal, divide by 100:

30% = 30 ÷ 100 = 0.30

To convert a decimal into a percentage, multiply by 100:

0.075 × 100 = 7.5%

How to Calculate Percentage

Percentage = (Part ÷ Whole) × 100

Example: Suppose you have 45 apples out of 60 apples.
Part = 45 | Whole = 60
(45 ÷ 60) × 100 = 75%
The answer is 75%.

How do you know which number is the whole?

The whole is normally the number associated with key terms like:

Total
Original amount
Out of
Cost price
Selling price
Revenue
Maximum marks

How to Calculate Percentage of a Number

Percentage of a number = (Percentage ÷ 100) × Number

Example 1: What is 15% of 240?
(15 ÷ 100) × 240
0.15 × 240 = 36
So, 15% of 240 is 36.

Example 2: What is 8% of 4,500?
(8 ÷ 100) × 4,500
0.08 × 4,500 = 360
So, 8% of 4,500 is 360.

How to Calculate Percentage of Marks

Marks Percentage = (Marks Obtained ÷ Total Marks) × 100

Example: If you obtained 68 marks out of 80:
(68 ÷ 80) × 100 = 85%
Your percentage is 85%.

How to Calculate Overall Exam Percentage

If you have several subjects, add your obtained marks together and add the maximum marks together.

Subject	Obtained	Total
English	82	100
Maths	91	100
Physics	78	100
Chemistry	88	100
Biology	99	100
Total	438	500

(438 ÷ 500) × 100 = 87.6%

Your overall percentage is 87.6%.

How to Calculate Percentage Change

Percentage Change = ((New − Old) ÷ Old) × 100

Use percentage change when you are comparing an old value with a new value.

How to Calculate Percentage Increase

Percentage Increase = (Increase ÷ Original) × 100

Example: A salary increases from 40,000 to 46,000.
Increase: 46,000 − 40,000 = 6,000
Percentage increase: (6,000 ÷ 40,000) × 100 = 15%
The salary increased by 15%.

How to Calculate Percentage Decrease

Percentage Decrease = (Decrease ÷ Original) × 100

Example: Traffic decreases from 12,500 visits to 9,500 visits.
Decrease: 12,500 − 9,500 = 3,000
Percentage decrease: (3,000 ÷ 12,500) × 100 = 24%
The decrease is 24%.

How to Calculate Discount Percentage

Discount % = ((Original Price − Sale Price) ÷ Original Price) × 100

Example: A jacket originally costs 2,500 and is now selling for 1,875.
Saving: 2,500 − 1,875 = 625
Discount: (625 ÷ 2,500) × 100 = 25%
The discount is 25%.

How to Calculate Profit Percentage

Profit = Selling Price − Cost Price

Profit Percentage = (Profit ÷ Cost Price) × 100

Example: You buy an item for 800 and sell it for 1,000.
Profit: 1,000 − 800 = 200
Profit percentage: (200 ÷ 800) × 100 = 25%
The profit percentage, or markup, is 25%.

How to Calculate Food Cost Percentage

Food Cost % = (Ingredient Cost ÷ Food Sales) × 100

How to Calculate Daily Interest on a Loan

Daily Interest = (Outstanding Principal × Annual Rate ÷ 100) ÷ 365

Common Percentage Mistakes

1. Dividing by the Wrong Number Always identify whether you need to divide by the whole, original value, or cost price.
2. Adding Successive Percentages A 40% discount followed by another 10% discount is 46%, not 50%.
3. Assuming Percentage Increases and Decreases Cancel A 20% decrease followed by a 20% increase results in 96, returning to 4% loss.

Frequently Asked Questions

What is the basic percentage formula?

The basic percentage formula is: Percentage = (Part ÷ Whole) × 100.

How do I calculate a percentage of a number?

Multiply the number by the percentage converted to a decimal: (Percentage ÷ 100) × Number.

How do I calculate percentage of marks?

Divide the marks obtained by the total marks and multiply by 100: (Marks Obtained ÷ Total Marks) × 100.

How do I calculate percentage increase?

Use: (Increase ÷ Original Value) × 100.

How do I calculate a discount percentage?

Subtract sale price from original price, divide by original price, and multiply by 100.

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