How to Calculate Percentage of a Number

Learn how to calculate what percentage a number represents of another number, with step-by-step examples and common use cases.

Introduction

Calculating percentages is one of the most practical math skills you can learn. Percentages appear everywhere—from discounts and taxes to statistics and growth rates.

Understanding how to calculate percentages will help you make better financial decisions and understand data. This guide will teach you the formulas and methods for all common percentage calculations.

Quick Reference

A percentage is a fraction of 100. 25% = 25/100 = 0.25

Always multiply by 100 to convert decimal to percentage!

What is a Percentage?

A percentage is a way of expressing a number as a fraction of 100. The word "percent" means "per hundred."

For example, 25% means 25 out of 100, or 25/100 = 0.25. Percentages make it easy to compare different quantities and understand proportions.

The Formula

To calculate what percentage a number represents of another number:

Percentage = (Part / Whole) × 100

To calculate a percentage of a number:

Result = (Number × Percentage) / 100

Step-by-Step Examples

Example 1: What percentage is 25 of 100?

Identify part and whole: Part = 25, Whole = 100
Apply formula: Percentage = (25 / 100) × 100
Calculate: Percentage = 0.25 × 100 = 25%

Answer: 25%

Example 2: What is 20% of 250?

Identify values: Number = 250, Percentage = 20
Apply formula: Result = (250 × 20) / 100
Calculate: Result = 5000 / 100 = 50

Answer: 50

Example 3: Real-World Discount

A $80 item is on sale for $60. What percentage discount is this?

Calculate discount amount: $80 - $60 = $20
Apply formula: Percentage = (20 / 80) × 100
Calculate: Percentage = 0.25 × 100 = 25%

Answer: 25% discount

You save $20 on a $80 item!

💡 Common Uses

Discounts

Calculate sale prices and savings

Tips

Calculate gratuity (typically 15-20%)

Taxes

Calculate tax amounts and totals

Statistics

Understand data and trends

⚠️ Common Mistakes

Forgetting to multiply by 100: Always multiply by 100 to convert decimal to percentage
Confusing part and whole: Make sure you know which number is the part and which is the whole
Using wrong formula: Use (Part/Whole)×100 for "what percentage", use (Number×Percent)/100 for "what is X% of Y"

When to Use a Calculator

Percentage calculators are helpful when:

Working with complex percentages or multiple calculations
Need quick, accurate results
Dealing with decimal percentages
Verifying manual calculations