Percentage Calculator

To calculate a percentage of any number, convert the percentage to a decimal by dividing by 100, then multiply by your number. For example, to find 25% of 200: first convert 25% to 0.25, then multiply 0.25 × 200 = 50. This method works for any percentage calculation, whether you're calculating discounts while shopping or determining tips at restaurants. The formula is: (Percentage ÷ 100) × Number = Result.

The easiest way to calculate percentages is to remember that "percent" means "per hundred," so any percentage can be written as a fraction over 100. For quick mental math, use common percentages: 10% is simply dividing by 10, 50% is dividing by 2, and 25% is dividing by 4. For example, 10% of 80 is 80 ÷ 10 = 8, and 50% of 120 is 120 ÷ 2 = 60. For more complex percentages like 18%, use our calculator above or multiply the number by 0.18 (80 × 0.18 = 14.4).

To calculate percentage increase or decrease, subtract the original value from the new value, divide by the original value, and multiply by 100. For example, if a stock price rises from $50 to $65, the increase is ((65 - 50) ÷ 50) × 100 = 30% increase. If it falls from $65 to $50, the decrease is ((50 - 65) ÷ 65) × 100 = -23.08% decrease. Notice that percentage decrease uses the higher original value as the denominator, which is why a 30% increase doesn't equal a 30% decrease when reversed. This calculation is essential for tracking financial changes, sales growth, and price fluctuations.

Percentage change measures the relative change from one value to another in a directional way, using the original value as the base. Percentage difference compares two values symmetrically without designating either as the "original." For example, comparing 80 and 100: the percentage change from 80 to 100 is ((100-80) ÷ 80) × 100 = 25% increase, while from 100 to 80 is -20% decrease. The percentage difference between them is (|100-80| ÷ ((100+80)÷2)) × 100 = 22.22%. Use percentage change when tracking progress or growth over time, and percentage difference when comparing two separate values objectively.

To find what percentage one number is of another, divide the first number by the second number, then multiply by 100. For example, to find what percentage 45 is of 180: (45 ÷ 180) × 100 = 25%. This means 45 is 25% of 180. This calculation is commonly used for determining test scores (if you got 85 out of 100 questions correct, that's 85%), calculating completion rates (15 tasks done out of 20 total means 75% complete), or analyzing portions of budgets and expenses.

To add a percentage to a number, first calculate the percentage amount, then add it to the original number. For example, to add 15% to 200: calculate 15% of 200 (200 × 0.15 = 30), then add: 200 + 30 = 230. To subtract a percentage, follow the same process but subtract instead: to subtract 20% from 150, calculate 20% (150 × 0.20 = 30), then subtract: 150 - 30 = 120. This is particularly useful for calculating discounted prices, price increases including tax, or salary adjustments.

Yes, percentages can be both greater than 100% and negative depending on the context. A percentage greater than 100% means the value is more than the whole - for example, if sales doubled from $100 to $200, that's a 100% increase, and if they tripled to $300, that's a 200% increase. Negative percentages indicate a decrease: if enrollment drops from 500 to 400 students, that's a -20% change. When expressing portions, percentages typically stay between 0% and 100%, but when measuring change, they can be any value. Understanding this is important for interpreting growth rates, stock market changes, and business metrics.

Common percentage calculation mistakes include forgetting to divide by 100 when converting percentages to decimals (using 25 instead of 0.25), mixing up the order of numbers in the formula, or using the wrong base value for percentage change calculations. For example, a 50% increase followed by a 50% decrease doesn't return you to the original value: starting with 100, increasing 50% gives 150, then decreasing 50% from 150 gives 75, not 100. Always verify you're using the correct formula for your specific calculation type, and double-check that you're dividing by the appropriate base number. Our calculator above handles these conversions automatically to prevent errors.

Percentages are used extensively in everyday situations: calculating store discounts and sale prices, determining tips at restaurants (typically 15-20%), understanding interest rates on loans and savings accounts, calculating tax amounts, tracking fitness goals and body fat percentage, analyzing test scores and grades, comparing prices and value (price per unit), evaluating investment returns, and understanding statistical data in news and research. For example, if a $50 item is 30% off, you save $15 and pay $35. Being comfortable with percentage calculations helps you make better financial decisions and understand numerical information you encounter daily.

Use percentages when communicating proportions to others (e.g., "25% discount"), decimals when doing calculations on a calculator or in spreadsheets (e.g., multiply by 0.25), and fractions for exact mathematical precision (e.g., 1/4 is exactly 25%). In practice, percentages are best for presenting information because they're intuitive (everyone understands 50% means half), decimals are best for computation (0.50 × 200 = 100), and fractions are best when exact ratios matter (mixing recipes, pharmaceutical dosing). Many situations use conversions: 25% = 0.25 = 1/4. For financial calculations, typically start with percentages, convert to decimals for multiplication, then convert results back to currency or percentages for reporting.