Percentage Calculator

Percentages represent a fraction of 100 and are calculated using three core formulas: 1. Finding X% of Y: Result = Y * (X / 100). For example, 15% of 200 = 200 * 0.15 = 30. 2. What percentage is X of Y: Result = (X / Y) * 100. For example, 30 is what % of 200? = (30/200) * 100 = 15%. 3. Percentage change: Result = ((New - Old) / |Old|) * 100. For example, from 200 to 250: ((250-200)/200) * 100 = 25% increase. The tool includes safety guards: division by zero returns an error message instead of Infinity, NaN inputs are detected and flagged, and Number.isFinite() validation ensures only valid results are displayed. All calculations use JavaScript's IEEE 754 double-precision floating-point arithmetic, providing approximately 15-17 significant decimal digits of precision.

1. Select the calculation type from the dropdown. 2. Enter the required values in the input fields. 3. The result appears instantly as you type. 4. Results include the formula used for educational reference. Available calculations: - What is X% of Y? - X is what % of Y? - Percentage change from X to Y - Percentage increase/decrease

Shopping Discounts: A 30% discount on a $80 item = $80 * 0.30 = $24 off, final price $56. Tax Calculations: 8.5% sales tax on $100 = $100 * 0.085 = $8.50, total $108.50. Grade Calculations: Scored 42 out of 50 = (42/50) * 100 = 84%. Investment Returns: Stock went from $150 to $180 = ((180-150)/150) * 100 = 20% gain. Tipping: 18% tip on a $75 bill = $75 * 0.18 = $13.50.