How do I calculate a percentage?

To find what percent A is of B: divide A by B and multiply by 100. For example, 25 is 50% of 50 because (25 ÷ 50) × 100 = 50%.

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Percentage Calculator

Solve any percentage problem: find a percentage, calculate what percent one number is of another, compute percentage difference between two values, or apply a percentage increase or decrease.

PercentagePercent ofDifferenceChangeMath

How to use this calculator

Choose the calculation type you need. For the main calculator, leave one field empty and fill the other two, then click Calculate. For common phrases and change calculators, fill in all fields and click Calculate.

Percentage Calculator

Provide any two values and click Calculate to find the third.

of=

Result

10% of 200 = 20

In-Depth Guide

A percentage calculator simplifies one of the most common mathematical operations in everyday life. Percentages express a number as a fraction of 100 and are used everywhere from calculating discounts and tips to understanding statistics and financial returns. Whether you need to find what percentage one number is of another, calculate a percentage increase or decrease, or determine a value after applying a percentage, this tool handles all scenarios instantly.

The word "percent" comes from the Latin "per centum," meaning "by the hundred." The concept has been used since ancient times, with Roman tax collectors using fractions of 100 for calculations. Today, percentages are fundamental in finance (interest rates, returns), retail (discounts, markups), statistics (survey results, probabilities), and science (concentrations, efficiencies).

Percentage change is particularly useful for comparing values over time. The formula is: ((New Value - Old Value) / Old Value) × 100. A positive result indicates an increase, while a negative result shows a decrease. For example, if a stock price rises from 0 to 5, the percentage increase is ((65-50)/50) × 100 = 30%.

Tips & Considerations

→To quickly estimate 10% of any number, simply move the decimal point one place to the left.
→For tip calculations, 15% is half of 10% plus 10%; 20% is simply double the 10% amount.
→When comparing percentage changes, always identify the base value clearly to avoid misleading interpretations.
→Percentage points and percentages are different: a rate going from 5% to 8% is a 3 percentage point increase but a 60% relative increase.
→Use percentage calculations to compare prices across different sizes or quantities to find the best value.

Frequently Asked Questions

The basic percentage formula is: Percentage = (Part / Whole) × 100. To find a percentage of a number: Result = (Percentage / 100) × Number. For percentage change: Change% = ((New - Old) / Old) × 100. These three formulas cover the vast majority of percentage calculations you will encounter.

Percentage Calculator in Common Phrases

Three common percentage expressions, each solved independently.

What is% of?

15% of 80 = 12

is what % of?

12 is 15% of 80

is% of what?

12 is 15% of 80

Percentage Difference Calculator

Calculate the percentage difference between two values.

Value 1

Value 2

Percentage Difference

50%

|10 − 6| / ((10 + 6) / 2) × 100 = 50%

Percentage Change Calculator

Calculate the result of increasing or decreasing a value by a given percentage.

=550

Result

550

Change: +50

500 increased by 10% = 550

About Percentages

A percentage is a number or ratio expressed as a fraction of 100, denoted by the symbol "%". It is one of the most common ways to express proportional relationships in everyday life — from discounts and interest rates to statistics and test scores. The word "percent" comes from the Latin per centum, meaning "by the hundred."

The fundamental formula is P × V1 = V2, where P is the percentage (as a decimal), V1 is the base value, and V2 is the result. Given any two of these three values, the third can be calculated.

Common Percentage Formulas

What is X% of Y? Multiply Y by X/100. For example, 15% of $80 = $80 × 0.15 = $12.
X is what % of Y? Divide X by Y and multiply by 100. For example, 12 is what % of 80? = (12/80) × 100 = 15%.
X is Y% of what? Divide X by (Y/100). For example, 12 is 15% of what? = 12 / 0.15 = 80.

Percentage Change vs. Percentage Difference

Percentage change measures how much a value has changed relative to its original value: (New − Old) / Old × 100. It is directional — a positive result means an increase, and a negative result means a decrease. For example, a price rising from $50 to $65 is a 30% increase.

Percentage difference measures the relative difference between two values when there is no defined "original" value: |V1 − V2| / ((V1 + V2) / 2) × 100. It is symmetric and always positive. This is useful when comparing two independent measurements.

Practical Applications

Percentages appear everywhere in daily life. In finance, interest rates, tax rates, and investment returns are all expressed as percentages. In retail, discounts and markups use percentage calculations. In health, body fat percentage and BMI classifications rely on percentages. Understanding how to calculate percentages accurately helps you make better financial decisions, interpret data correctly, and avoid common mathematical pitfalls.

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