Percentage Calculator – Calculate Percentages, Increase & Decrease

Percentages are used in many parts of everyday life. You may need to calculate your exam marks, a discount on a product, a salary increase, tax, profit, business growth, or the percentage change between two numbers.

Doing these calculations by hand is possible, but it can take time and mistakes are easy to make. A percentage calculator gives you a quick way to get the answer and understand how the calculation works.

Modern percentage calculators commonly support several problems, including finding a percentage of a number, finding what percentage one number is of another, and calculating percentage increases or decreases.

What Is a Percentage?

A percentage means “per hundred.” The symbol used for percentage is %.

For example:

• 10% means 10 out of 100.
• 25% means 25 out of 100.
• 50% means 50 out of 100.
• 75% means 75 out of 100.
• 100% means the complete amount.

You can also write a percentage as a decimal:

The basic idea is simple: a percentage tells you how large one amount is compared with 100.

What Can a Percentage Calculator Do?

A good percentage calculator should handle the most common percentage questions instead of making you use a different tool for every calculation.

These are among the most common percentage problems people search for and use in school, work, shopping, business, and everyday calculations.

How to Use a Percentage Calculator

Using a percentage calculator is usually very simple.

Step 1: Choose the type of percentage calculation you need.

Step 2: Enter the numbers into the required fields.

Step 3: Click the calculate button.

Step 4: Check the result and, when available, review the formula or calculation steps.

For example, suppose you want to know 20% of 250.

Enter:

• Percentage = 20
• Number = 250

The result is:

20% of 250 = 50

A useful calculator should make the result easy to understand instead of showing only a final number.

How to Calculate a Percentage of a Number

One of the most common percentage questions is:

What is X% of Y?

Use this formula:

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

Example

What is 15% of 200?

First convert 15% to a decimal:

15 ÷ 100 = 0.15

Then multiply:

0.15 × 200 = 30

So:

15% of 200 = 30

You can use the same method for almost any number.

How to Find What Percentage One Number Is of Another

Sometimes you know the part and the total, but you need to find the percentage.

Use:

Percentage = (Part ÷ Whole) × 100

Example

You scored 72 marks out of 90. What percentage did you get?

72 ÷ 90 = 0.8

0.8 × 100 = 80%

Therefore:

72 out of 90 = 80%

This calculation is useful for exam results, test scores, sales targets, attendance, surveys, and many other situations.

How to Calculate Percentage Increase

A percentage increase tells you how much a number has gone up compared with its original value.

The formula is:

Percentage Increase = ((New Value − Original Value) ÷ Original Value) × 100

Example

A product price increases from $80 to $100.

First find the increase:

100 − 80 = 20

Then divide by the original price:

20 ÷ 80 = 0.25

Multiply by 100:

0.25 × 100 = 25%

So the price increased by 25%.

The important point is that percentage increase uses the original value as the starting point.

How to Calculate Percentage Decrease

A percentage decrease shows how much a value has gone down compared with its original value.

You can use:

Percentage Decrease = ((Original Value − New Value) ÷ Original Value) × 100

Example

A product costs $200 and later costs $150.

Difference:

200 − 150 = 50

Now calculate:

50 ÷ 200 × 100 = 25%

Therefore, the price decreased by 25%.

The same general percentage-change calculation can also produce a negative result when the new value is lower than the original value.

Percentage Increase and Decrease Examples

Here are some simple examples:

Always pay attention to the original value. This is important because a 20% increase and a 20% decrease do not always cancel each other out.

For example, increasing 100 by 50% gives 150. Decreasing 150 by 50% gives 75, not 100.

How to Add a Percentage to a Number

You may want to increase a number by a specific percentage.

For example:

Increase $500 by 20%.

First find 20% of $500:

20% of 500 = 100

Then add it:

500 + 100 = 600

So:

$500 increased by 20% = $600

You can also use the shorter formula:

New Value = Original Value × (1 + Percentage ÷ 100)

For the example:

500 × 1.20 = 600

This method is useful for price increases, salary increases, business growth, and markups.

How to Remove a Percentage From a Number

You can also decrease a number by a percentage.

For example:

Decrease 500 by 20%.

20% of 500 = 100

500 − 100 = 400

Therefore:

500 decreased by 20% = 400

The formula is:

New Value = Original Value × (1 − Percentage ÷ 100)

So:

500 × 0.80 = 400

How to Calculate Discounts

Percentage calculations are especially useful when shopping.

Suppose a jacket costs $120 and has a 25% discount.

First calculate the discount:

25% of $120 = $30

Then subtract the discount:

$120 − $30 = $90

The sale price is therefore $90.

A percentage calculator can make these calculations much faster and reduce simple arithmetic errors.

How to Calculate Exam Marks Percentage

Students often use percentage calculations to find their exam results.

The formula is:

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

Example

You receive 450 marks out of 600.

450 ÷ 600 × 100 = 75%

Your result is:

75%

You can use the same formula for school tests, college exams, quizzes, assignments, and other scores.

Percentage Calculator for Salary Increases

Percentage calculations are also useful for salary changes.

Suppose your salary was $2,000 and increases to $2,300.

Difference:

$2,300 − $2,000 = $300

Percentage increase:

($300 ÷ $2,000) × 100 = 15%

Your salary increased by 15%.

You can use the same calculation for pay raises, hourly rates, commissions, business revenue, and other financial comparisons.

Percentage Calculator for Tax and Markups

Businesses and shoppers may also need percentages to calculate taxes, fees, or markups.

For example, suppose an item costs $1,000 and a 10% charge is added.

10% of $1,000 = $100

$1,000 + $100 = $1,100

The final amount is $1,100.

The exact tax rate depends on the country, product, and applicable rules, so a calculator should be used for the mathematics rather than assuming one tax rate applies everywhere.

Percentage Change vs Percentage Difference

These terms can look similar, but they can answer different questions.

Percentage change normally compares a new value with an original or starting value.

Percentage difference is generally used when comparing two values without choosing one as the starting point.

For example, if a price changes from 100 to 120, percentage change uses 100 as the baseline:

(120 − 100) ÷ 100 × 100 = 20%

This distinction matters because changing the baseline can change the percentage result.

Common Percentage Calculation Mistakes

Percentage problems are simple once you understand the formula, but several mistakes happen often.

Using the wrong base number

For percentage increase or decrease, the original value is normally the baseline.

Forgetting to divide by 100

20% means 20 ÷ 100, or 0.20.

Confusing percentage with percentage points

A change from 10% to 15% is a 5 percentage-point increase. It is also a 50% increase relative to the original 10%. These describe different things.

Assuming equal increases and decreases cancel

A 50% increase followed by a 50% decrease does not return to the original amount.

Rounding too early

When working with decimals, rounding intermediate numbers too soon can slightly change the final result. A calculator can keep more precision until the final answer.

Why Use an Online Percentage Calculator?

An online percentage calculator can be useful when you need a quick answer without manually working through a formula.

It can help with:

• Exam marks
• Discounts
• Shopping prices
• Salary increases
• Business calculations
• Tax calculations
• Profit and loss
• Percentage increases
• Percentage decreases
• Comparing numbers
• Everyday math

The biggest benefit is convenience. Instead of remembering several formulas, you can enter the values and let the calculator perform the calculation.

For learning, however, it is still useful to understand the formula behind the answer. This helps you check whether the result makes sense.

Percentage Formulas at a Glance

Keep these common formulas handy:

These formulas cover many of the percentage questions people commonly ask.

Quick Percentage Examples

Here are some quick examples you can use to check your understanding:

What is 10% of 250?
Answer: 25

What is 25% of 400?
Answer: 100

50 is what percentage of 200?
Answer: 25%

A price changes from 100 to 125. What is the increase?
Answer: 25%

A price changes from 200 to 150. What is the decrease?
Answer: 25%

What is 15% of 800?
Answer: 120

You scored 80 out of 100. What is your percentage?
Answer: 80%

Frequently Asked Questions

What is a percentage?

A percentage is a number expressed as a part of 100. For example, 25% means 25 out of 100.

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply the result by the number. For example, 20% of 150 is 0.20 × 150 = 30.

How do I calculate what percentage one number is of another?

Divide the part by the whole and multiply by 100. For example, 40 out of 80 is (40 ÷ 80) × 100 = 50%.

How do I calculate percentage increase?

Subtract the original value from the new value, divide by the original value, and multiply by 100.

Formula:
((New − Original) ÷ Original) × 100

How do I calculate percentage decrease?

Subtract the new value from the original value, divide by the original value, and multiply by 100.

Formula:
((Original − New) ÷ Original) × 100

How do I calculate exam percentage?

Divide your marks by the total marks and multiply by 100.

For example, 450 out of 600:

450 ÷ 600 × 100 = 75%

Can a percentage be more than 100%?

Yes. A percentage can be greater than 100%. For example, if a value increases from 100 to 300, the increase is 200%.

What is the difference between percentage and percentage points?

Percentage points describe the direct difference between two percentages. Percentage change compares the difference with the starting percentage.

Why do percentage increase and decrease use the original value?

The original value provides the baseline for measuring the change. Using a different baseline can produce a different percentage.

Conclusion

A percentage calculator makes common percentage problems faster and easier. Whether you are calculating exam marks, finding a discount, checking a salary increase, comparing two numbers, or calculating a percentage change, the basic formulas are straightforward once you understand the starting value and what you are trying to find.

The most important formulas to remember are (percentage ÷ 100) × number, (part ÷ whole) × 100, and ((new − original) ÷ original) × 100 for percentage change. A calculator can handle the arithmetic quickly while showing the result in a clear format.

For your calculator website, the most useful approach is to place the Percentage Calculator tool before this educational content, then use this article to answer the common questions users have about percentages. This creates a useful combination of an interactive tool and supporting information rather than a page containing only a calculator.