The Three Percentage Formulas

Percentages are one of the most commonly used mathematical concepts in daily life. This calculator covers the three most frequent percentage calculations you will encounter.

1. What is X% of Y?

Formula: Result = (X ÷ 100) × Y. Use this when you know the percentage and the total, and need to find the portion. Example: What is 25% of 200? Answer: 50.

2. X is what % of Y?

Formula: Percentage = (X ÷ Y) × 100. Use this when you know the part and the whole, and need to find what percentage the part represents. Example: 50 is what percent of 200? Answer: 25%.

3. Percentage change from X to Y

Formula: Change = ((Y - X) ÷ |X|) × 100. Use this to find how much something increased or decreased. A positive result means an increase; negative means a decrease. Example: From 80 to 100 = +25% change.

Real-World Applications

• Sales tax: 8% of $50 = $4.00 tax
• Grade calculations: 42 out of 50 = 84%
• Price changes: $80 to $100 = 25% increase
• Tip calculation: 18% of $85 = $15.30 tip
• Discount savings: 30% off $120 = $36 saved