Percentage Calculator
Calculate percentages, increases, discounts, and percentage changes easily.
What is X% of Y?
Result
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What is a percentage?
A percentage is a way to express a proportion as a fraction of 100. The '%' symbol comes from the Latin 'per centum' (per hundred). For example, 25% means 25 out of 100, or the fraction 25/100 = 0.25. Percentages are fundamental in finance, statistics, sciences, and everyday life.
Basic percentage formulas
Percentage operations follow simple formulas: To calculate X% of Y: (X/100) × Y. To increase Y by X%: Y × (1 + X/100). To decrease Y by X%: Y × (1 - X/100). For percentage change from A to B: ((B - A) / A) × 100.
Practical examples
Shopping: a 20% discount on $80 is 80 × 0.20 = $16 savings (you pay $64). Taxes: 8% sales tax on $100 adds $8 (total $108). Tips: 15% tip on a $45 bill is $6.75. Grades: 18 out of 20 points is (18/20) × 100 = 90%.
Common percentage errors
The most common mistake is confusing percentage points with percentages. If a rate rises from 5% to 7%, it increased by 2 percentage points, but the percentage increase is 40% ((7-5)/5 × 100). Another error: thinking a 50% discount followed by a 50% increase returns to the original price (it doesn't: 100 → 50 → 75).