Percentage Calculator: Formulas, Examples & Tips

Percentages are everywhere — from discounts and tips to interest rates and statistics. Knowing how to calculate percentages quickly is a valuable everyday skill.

Common Percentage Calculations

What Is X% of Y?

Multiply Y by X/100. Example: What is 15% of 200?

200 × (15/100) = 30

X Is What Percent of Y?

Divide X by Y and multiply by 100. Example: 45 is what percent of 180?

(45 / 180) × 100 = 25%

Percentage Increase or Decrease

Change (%) = ((New - Old) / Old) × 100

Example: Price went from $80 to $100.

((100 - 80) / 80) × 100 = 25% increase

Percentage Formulas Reference

Calculation	Formula	Example
X% of Y	Y × (X/100)	20% of 150 = 30
X is what % of Y	(X/Y) × 100	30 is 20% of 150
% increase	((New-Old)/Old) × 100	80→100 = 25%
% decrease	((Old-New)/Old) × 100	100→80 = 20%
Add X%	Value × (1 + X/100)	100 + 10% = 110
Subtract X%	Value × (1 - X/100)	100 - 10% = 90

Practical Applications

Shopping: Calculate discounts — 30% off a $50 item = $15 savings

Finance: Interest rates on loans and investments

Health: Body fat percentage, nutritional values

Education: Grade calculations and test scores

Business: Profit margins, growth rates, tax calculations

Try It Yourself

Use our free Percentage Calculator to perform any percentage calculation instantly — no formulas needed.