Calculated using standard mathematical and industry formulas.
Calculate percentages by dividing the part by the total and multiplying by 100: Percentage = (Part / Whole) × 100. To find percentage increase or decrease between two numbers, use the percentage change formula: Percentage Change = ((New Value - Old Value) / Old Value) × 100.
How to use this calculator?
Choose the question you are answering: what is X% of Y, X is what percent of Y, or the change from X to Y.
Enter the two values — the answer appears instantly with the calculation written out.
Switch modes to sanity-check a result from another angle (a discount and its final price should agree).
Use Share to send the exact calculation; the link keeps your numbers.
Percentage change is positive for an increase and negative for a decrease. Division by zero is not defined, so Y (or From) must not be 0 in the last two modes.
Step-by-step calculation example
15% of 200 = (15 ÷ 100) × 200 = 30. And going from 100 to 125 is a +25% change.
Key insights to remember
Percent means 'per hundred': 15% is 15 ÷ 100, or 0.15 as a decimal — multiplying by it takes the percentage directly.
Percentage changes are not symmetric: a 50% loss needs a 100% gain to get back to the start.
Percentage points and percent are different: going from 10% to 12% is +2 points but a +20% relative change.
Sequential discounts do not add up: 20% off then 10% off is 28% off in total, not 30%.
To undo a 25% increase you must decrease by 20%, not 25% — the base has changed.
How to interpret your results?
Percent vs. Percentage Points
Moving from 10% to 12% is an increase of 2 percentage points, but represents a 20% relative percentage increase in the underlying rate.
Expert advice & guidance
💡 Mental math shortcut: To quickly calculate 15% (e.g. for tipping), find 10% by shifting the decimal point one place left, then add half of that amount.
Frequently asked questions
How do you calculate a percentage of a number?
Multiply the number by the percentage and divide by 100: Result = (Number × Percentage) / 100. E.g., 20% of 150 = (150 × 20) / 100 = 30.
How to calculate percentage increase or decrease between two values?
Percentage Change = ((New Value - Old Value) / Old Value) × 100. Positive results indicate increase; negative results indicate decrease.
What is the difference between percent change and percentage points?
Percent change measures relative change in value; percentage points measure simple arithmetic difference between two percentage rates.
How to calculate discount price percent off?
Discount Price = Original Price × (1 - Discount Percentage / 100). E.g., $80 with 25% off = $80 × 0.75 = $60.
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