How to Calculate Percentages

What is a Percentage?

A percentage is a way of expressing a number as a fraction of 100. The word comes from the Latin "per centum," meaning "by the hundred." The symbol % represents percentages.

The Basic Formula

Percentage = (Part / Whole) × 100

Common Percentage Calculations

1. Finding a Percentage of a Number

Example: What is 25% of 80?

25% of 80 = (25/100) × 80 = 0.25 × 80 = 20

2. Finding What Percentage One Number is of Another

Example: 15 is what percent of 60?

(15 / 60) × 100 = 0.25 × 100 = 25%

3. Percentage Increase

Formula: ((New - Old) / Old) × 100

Example: Price increased from $40 to $50

((50 - 40) / 40) × 100 = (10/40) × 100 = 25% increase

4. Percentage Decrease

Example: Price dropped from $100 to $75

((100 - 75) / 100) × 100 = 25% decrease

Quick Mental Math Tips

10% — Divide by 10 (move decimal left)
5% — Half of 10%
25% — Divide by 4
50% — Divide by 2
1% — Divide by 100

Use Our Calculator

Try our Percentage Calculator for quick calculations!