Math

Percentages Made Easy: A Practical Guide

From discounts to tips, percentages are everywhere. Master the basics of percentage increase and decrease with this easy guide.

Neha Kapoor

October 22, 2025

5 min read

Percentages are the universal language of comparison. Whether you are shopping during a sale or calculating a tip at dinner, understanding how to work with percentages is an essential life skill. Let's demystify the math.

The Basics: What is a Percentage?

The word "percent" comes from the Latin per centum, meaning "by the hundred." Essentially, a percentage is a fraction with a denominator of 100.

For example, 50% means 50 out of 100, or roughly half.

Calculating Percentage Increase

Want to know how much a price has gone up? Here is the formula:

(New Number - Original Number) ÷ Original Number × 100

Example: A ticket price rose from $40 to $50.
($50 - $40) = $10
$10 ÷ $40 = 0.25
0.25 × 100 = 25% Increase

Calculating Percentage Decrease

Great for figuring out discounts! The formula is similar:

(Original Number - New Number) ÷ Original Number × 100

Quick Tips for Mental Math

To find 10%, just move the decimal point one place to the left. (10% of 50.0 is 5.0)
To find 5%, find 10% and cut it in half.
To find 20%, find 10% and double it.