How to Calculate a Percentage?

Percentages are a quick way to compare numbers, track changes, and understand proportions. Whether you're figuring out a sale discount, a test score, or a tip at a restaurant, calculating a percentage makes life easier. 

But what is a percentage? How do you calculate it? You can do it manually with a simple formula or use our instant percentage calculator to get results in seconds—perfect for when you need a quick answer without the math! Read on to find out more in our detailed guide.

What is a percentage?

A percentage is a way to express a number as a fraction of 100. It is frequently used to express a fraction of a whole or to compare two values and is typically represented by the "%" symbol. It is commonly used to compare proportions, measure changes, and calculate statistics.

What is a percentage?

If you scored 85% on your Math test, it means you got 85 out of 100 questions correct. 

How do I calculate a percentage?

To calculate a percentage, use this simple formula:

Percentage = (Part​ ÷ Total) × 100

For example

Let’s say you have 10 cookies, and you eat 4 of them. Want to find the percentage you ate?

• Divide the part (cookies eaten) by the total (all cookies): 4 ÷ 10 = 0.40
• Multiply by 100: 0.40 × 100 = 40%

So, you ate 40% of the cookies.

How is a percentage used?

Percentages are a part of everyday life, helping us understand proportions, compare values, and make smarter financial decisions. Here are some real-life examples of how percentages are used:

Shopping

Imagine you find a jacket on sale for 25% off its original price of $200. To find your savings:

• Multiply the discount percentage by the original price: 200 × 0.25 = 50
• You save $50, and the new price is $150.

Sales and discounts often use percentages to show how much you’re saving at checkout.

Finance & Banking

Percentages are essential in banking, especially when dealing with interest rates. If your bank offers 3% annual interest on a $1,000 savings account:

• Multiply your balance by the interest rate: 1000 × 0.03 = 30
• You earn $30 in interest for the year.

The higher the percentage, the more you earn on your savings.

Health & Nutrition

Ever checked a food label and seen "10% sugar" on a juice bottle? This means that in 100 grams of juice, 10 grams are sugar.

Good to know

For example, if the bottle contains 500g of juice:

• Multiply the total weight by 10% (0.10): 500 × 0.10 = 50
• The bottle has 50 grams of sugar in total.

Understanding percentages in nutrition helps you make healthier choices. From calculating tips at restaurants to tracking sports statistics, percentages are everywhere!

How do I calculate a percentage increase?

A percentage increase tells you how much something has grown compared to its original value.

Formula:

Percentage Increase = ((New Value − Old Value​) ÷ Old Value) × 100

For example

Imagine your phone bill was $50, but this month it’s $65.

• Find the difference: 65 − 50 = 15
• Divide by the original value: 15 ÷ 50 = 0.30
• Multiply by 100: 0.30 × 100 = 30%

Your phone bill increased by 30%.

How do I calculate a percentage decrease?

A percentage decrease tells you how much something has reduced from its original value.

Formula:

Percentage Decrease = ((Old Value − New Value​) ÷ Old Value) × 100

For example

A jacket was originally $80, but it’s on sale for $60.

• Find the difference: 80 − 60 = 20
• Divide by the original price: 20 ÷ 80 = 0.25
• Multiply by 100: 0.25 × 100 = 25%

The jacket is 25% off.

How do I calculate a reverse percentage?

A reverse percentage helps you find the original value before a percentage change.

For example

You bought a laptop for $900 after a 10% discount, but you want to know the original price.

Since the price after the discount is 90% of the original, divide by 0.90:

900 ÷ 0.90 = 1000

So, the original price before the discount was $1,000.

How do I calculate GPA from a percentage?

In the U.S., Grade Point Average (GPA) is commonly calculated on a 4.0 scale, where A is the highest grade (4.0) and F is the lowest (0.0). If you have your percentage score, you can estimate your GPA using a conversion chart or formula.

Converting a Single Percentage to GPA

Let's say your final grade in Math is 85%. Looking at the chart, this falls in the B range, which corresponds to a GPA of around 3.5.

If you have grades in five subjects, you can convert each one to GPA and then find the average.

How to calculate GPA from percentage?

• Step 1: Add up the GPAs: 4.0 + 3.5 + 2.5 + 3.7 + 3.0 = 16.7
• Step 2: Divide by the number of subjects 16.7 ÷ 5 = 3.34

So, your final GPA is 3.34.

Some schools use a weighted GPA system where AP, Honors, or IB courses are graded on a 5.0 scale instead of 4.0. In this case, an A in an advanced class could be 5.0 instead of 4.0, making your GPA higher.