Percentage Calculator

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Percentage Calculator Quick & Accurate

A% of B · What % is A of B? · Percent Change · After % Increase/Decrease · How to use · FAQ · Related tools

Percentage Calculator
A% of B, what percent is A of B, percent change, and after % increase/decrease.

A% of B

Formula: (A ÷ 100) × B

How to Use the Percentage Calculator

Our percentage calculator offers five different calculation modes to handle various percentage-related problems. Simply select the tab that matches your calculation needs and enter the required values.

Calculate percentages, percentage change, increase/decrease, and more with our free online tool. Includes step-by-step explanations and formulas.

Three Simple Calculation Modes

1. Percentage of a Number: Find what X% of Y is (e.g., what is 15% of 200?).

2. Percentage Change: Calculate the percentage increase or decrease between two values.

3. Percentage Increase/Decrease: Find the new value after increasing or decreasing by a certain percentage.

4. Reverse Percentage: Find the original value before a percentage increase or decrease was applied.

Percentage Fundamentals: Definitions and Formulas

What Does 'Percent' Mean?

The word "percent" comes from the Latin "per centum," meaning "by the hundred." A percentage is a way of expressing a number as a fraction of 100. It is denoted using the percent sign (%).

The Core Formula: Finding X% of Y

The fundamental percentage formula is:

Percentage = (Value / Total Value) × 100

Or to find a percentage of a number:

Result = (Percentage / 100) × Number

Step-by-Step Manual Calculations

Example 1: Calculating Percentage of a Whole

To find 25% of 80:

Step 1: Convert 25% to a decimal: 25 ÷ 100 = 0.25

Step 2: Multiply the decimal by the number: 0.25 × 80 = 20

Answer: 25% of 80 is 20

Example 2: Calculating Percentage Increase (Growth Rate)

If a product's price increases from $50 to $65:

Step 1: Find the difference: $65 - $50 = $15

Step 2: Divide the difference by the original value: $15 ÷ $50 = 0.3

Step 3: Multiply by 100 to get percentage: 0.3 × 100 = 30%

Answer: The price increased by 30%

Example 3: Calculating Percentage Decrease (Discounts)

If an item originally priced at $80 is on sale for $64:

Step 1: Find the difference: $80 - $64 = $16

Step 2: Divide the difference by the original value: $16 ÷ $80 = 0.2

Step 3: Multiply by 100 to get percentage: 0.2 × 100 = 20%

Answer: The discount is 20%

Example 4: The Reverse Percentage Calculation

If you know the final price after a 15% discount is $85:

Step 1: The final price represents 85% of the original (100% - 15%)

Step 2: Divide the final price by the percentage in decimal form: $85 ÷ 0.85 = $100

Answer: The original price was $100

Real-World Percentage Applications

Financial Applications (Interest, Tax, CPI)

Percentages are crucial in finance for calculating interest rates on loans and savings, determining sales tax or VAT, and understanding inflation through the Consumer Price Index (CPI).

Everyday Use (Tipping, Sales Discounts)

Calculate appropriate tips at restaurants (typically 15-20%), determine final prices during sales, and compare product discounts to make informed purchasing decisions.

Academic and Statistical Use (Grades, Error Margin)

In education, percentages calculate grades and score improvements. In statistics, they express margins of error, confidence intervals, and proportional relationships in data.

Percentage Calculator – Frequently Asked Questions

Convert the percentage to a decimal by dividing by 100, then multiply by the number. (Example: 25% of 80 → 0.25 × 80 = 20.)

Subtract the original from the new value, divide that difference by the original value, then multiply by 100.

Divide the numerator by the denominator to get a decimal, then multiply by 100.

Percentage change is relative to the starting value; percentage difference is relative to the average of the two values.

Subtract 30% from 100% to get 70%, then multiply the original price by 0.70.

Divide the final amount by the remaining percentage in decimal form. (Example: original = final ÷ 1.20 for a 20% tax.)

It evolved from shorthand for "per cento" (per hundred) used in the 17th century.

Break the percent into simple parts (e.g., 15% = 10% + 5%). Find 10% by moving the decimal one place left, then add half of that for 5%.