📖 How to Calculate Percentages
What is X% of Y?
Multiply the number by the percentage divided by 100: Y × (X/100)
Example: 15% of 200 = 200 × 0.15 = 30
X is what percent of Y?
Divide X by Y and multiply by 100: (X/Y) × 100
Example: 30 is what % of 150? = (30/150) × 100 = 20%
Percentage Change
((New - Old) / Old) × 100
Example: From 80 to 100 = ((100-80)/80) × 100 = 25% increase
📐 Percentage Formulas
❓ Frequently Asked Questions
Use these tricks: 10% = move decimal left. 5% = half of 10%. 15% = 10% + 5%. 20% = double 10%. For 17% of 50, find 50's 10% (5) + 5% (2.5) + 2% (1) = 8.5.
Percentage is a portion out of 100. Percentile shows your rank relative to others (90th percentile = better than 90% of people).
The second discount applies to the already-reduced price. 50% off $100 = $50. Another 50% off $50 = $25. Total: 75% off, not 100%!
Divide the numerator by denominator, then multiply by 100. Example: 3/4 = 0.75 × 100 = 75%