Percentage Calculator

Solve common percentage problems instantly, from finding discounts to calculating percentage differences and changes.

What is

Understanding Percentages

What Is a Percentage?

A percentage expresses a number as a part of 100. The word percent means per hundred, so 25% means 25 out of 100, which can also be written as 25/100 or 0.25.

A percentage calculator helps solve real-life problems such as discounts, exam scores, sales tax, tips, loan interest, investment returns, salary raises, business profit, and data reports.

Calculator Uses

What Does a Percentage Calculator Do?

A percentage calculator solves common percentage problems automatically, so you can enter the known numbers and quickly get the answer.

Percent of a number: Answers questions like: What is 15% of 200? This is useful for discounts, taxes, tips, commissions, exam marks, interest, and budgets.
Part as a percent of whole: Answers questions like: 45 is what percent of 60? This is useful for grades, attendance, conversion rates, and progress tracking.
Percentage difference: Compares two values without treating either value as the original starting point.
Percentage change: Shows how much a value increased or decreased compared with the original value.

The Math

Basic Percentage Formulas

Most percentage problems come from a few core formulas. These formulas cover percent of a number, percent of a whole, reverse percentages, changes, and differences.

Percentage value

\text{Percentage Value} = \frac{\text{Number} \times \text{Percentage}}{100}

Example: 30% of 250 = 250 x 30 / 100 = 75.

Part as a percent of whole

\text{Percentage} = \frac{\text{Part}}{\text{Whole}} \times 100

Example: 45 is what percent of 60? 45 / 60 x 100 = 75%.

Find the whole

\text{Whole} = \frac{\text{Part}}{\text{Percentage}} \times 100

Example: 80 is 40% of what number? 80 / 40 x 100 = 200.

Percentage change

\text{Percentage Change} = \frac{\text{New} - \text{Old}}{\text{Old}} \times 100

If the result is positive, it is an increase. If it is negative, it is a decrease.

Percentage difference

\text{Percentage Difference} = \frac{|A-B|}{(A+B)/2} \times 100

Use this when comparing two values without treating one as the original value.

Specific Calculators

Common Percentage Calculator Problems

These formulas cover the most common search intents for percentage calculator users.

Problem	Formula	Example
Percentage increase	$\frac{\text{New}-\text{Old}}{\text{Old}}\times100$	$100 to $125 = 25% increase
Percentage decrease	$\frac{\text{Old}-\text{New}}{\text{Old}}\times100$	$80 to $60 = 25% decrease
Discount	$\frac{\text{Price}\times\text{Discount \%}}{100}$	$120 with 25% off saves $30
Sales tax	$\frac{\text{Price}\times\text{Tax Rate}}{100}$	$200 with 8% tax adds $16
Tip	$\frac{\text{Bill}\times\text{Tip \%}}{100}$	$75 bill with 20% tip adds $15
Marks percentage	$\frac{\text{Obtained}}{\text{Total}}\times100$	432 out of 500 = 86.4%
Profit percentage	$\frac{\text{Selling Price}-\text{Cost Price}}{\text{Cost Price}}\times100$	$80 cost, $100 sell = 25% profit

Core Concepts

Percent vs. Percentage Points

Percent and percentage points are not the same, and this matters in finance, statistics, polls, interest rates, and news reports.

If an interest rate increases from 4% to 5%, it increased by 1 percentage point. The relative percentage increase is 25% because (5 - 4) / 4 x 100 = 25%.

Conversions

Percent to Decimal and Decimal to Percent

Percentages and decimals are closely connected, and converting between them is often the first step in manual percentage math.

Percent to decimal

\text{Decimal} = \frac{\text{Percent}}{100}

Example: 25% = 25 / 100 = 0.25.

Decimal to percent

\text{Percent} = \text{Decimal} \times 100

Example: 0.75 x 100 = 75%.

How to Use

How to Use This Percentage Calculator

Choose the percentage calculation type, enter the known numbers, click calculate, then review the answer.

1
Choose the calculation type
Use percent of a number, common phrases, percentage difference, or percentage change.
2
Enter the known values
Use the fields shown for the selected mode.
3
Calculate and compare
Review the result, then switch modes if you need another percentage calculation.

Mistakes

Common Percentage Calculator Mistakes

Percentage errors usually happen because the base value changes, the wrong formula is chosen, or rounding happens too early.

Confusing increase and difference: Percentage increase uses the original value as the base. Percentage difference usually uses the average of the two values as the base.
Using the new value as the base: For percentage change, the old value should usually be the base.
Forgetting to divide by 100: To calculate 20% of a number, use 20 / 100 = 0.20 before multiplying.
Adding percentages directly: A 10% increase followed by a 10% decrease does not return to the original number. 100 + 10% = 110, then 110 - 10% = 99.
Confusing percent and percentage points: A change from 5% to 6% is 1 percentage point, but the relative increase is 20%.
Rounding too early: Rounding in the middle of a calculation can slightly change the final result.

Real-Life Uses

Where Percentages Are Used

Percentages are useful because they put different values on the same scale: out of 100.

Area	Use
Shopping	Discounts, sale prices, coupons, cashback, and sales tax
School	Exam percentage, assignment scores, grade percentage, and marks
Business	Profit margin, markup, revenue growth, conversion rate, and targets
Finance	Investment returns, interest rates, inflation, tax rates, and salary raises
Health and fitness	Weight change, calorie percentages, body composition, and progress
Data and reports	Survey results, growth rates, error rates, and comparison percentages

Percentage Calculator FAQ

Frequently Asked Questions

A percentage calculator is a tool that solves percentage problems such as finding a percent of a number, calculating percentage increase or decrease, and finding what percent one number is of another.

A percentage is a number expressed as a part of 100. For example, 40% means 40 out of 100.

Use this formula: Y x X / 100. Example: 20% of 150 = 150 x 20 / 100 = 30.

Use this formula: Part / Whole x 100. Example: 30 is what percent of 150 = 30 / 150 x 100 = 20%.

Use this formula: (New Value - Old Value) / Old Value x 100.

Use this formula: (Old Value - New Value) / Old Value x 100.

Percentage difference compares two values by dividing their absolute difference by their average, then multiplying by 100.

Divide the percentage by 100. Example: 25% = 0.25.

Percent is a relative comparison. Percentage points are the direct difference between two percentages. For example, 4% to 5% is a 1 percentage point increase but a 25% relative increase.

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