What is X% of Y?
Percentage Increase
Percentage Decrease
What is a Percentage?
A percentage is a way of expressing a number as a fraction of 100. It's commonly used to compare proportions, calculate discounts, track growth, and analyze data in everyday life, business, and academics.
Key Formulas
X% of Y: (X ÷ 100) × Y
Increase: ((New - Old) ÷ Old) × 100
Decrease: ((Old - New) ÷ Old) × 100
When calculating percentage change, always use the original value as your denominator. A 50% increase followed by a 50% decrease doesn't return to the original value—math is tricky!
Quick Reference
Common Percentages
Real-World Uses
Percentage calculations are essential for: calculating sales tax and discounts, understanding interest rates, analyzing business growth, interpreting statistics, grading systems, and making informed financial decisions in daily life.