Five Percentage Calculations
Each panel handles one common type of percentage problem. All five update in real time as you type. You can use decimals in any field.
Panel 1 (X% of Y): multiply Y by X/100. Used for tips, discounts, and tax calculations.
Panel 2 (X is what % of Y): divide X by Y and multiply by 100. Used to find a grade percentage or a market share.
Panel 3 (Percentage Change): (new - old) / |old| × 100. Positive = increase, negative = decrease.
Panel 4 (Percentage Difference): |X - Y| / ((X+Y)/2) × 100. Symmetric; useful when there is no clear "before" and "after".
Panel 5 (Add/Subtract %): adds or subtracts a percentage of the original value from itself.
Frequently Asked Questions
Multiply the number by the percentage divided by 100. For example, 15% of 200 = 200 × 0.15 = 30. Panel 1 of this calculator handles this automatically: enter the percent and the number, and the result is shown instantly.
Divide the first number by the second, then multiply by 100. For example, 30 is what percent of 200? 30 ÷ 200 × 100 = 15%. Use Panel 2 of this calculator for this type of problem.
Percentage change = ((new value - old value) / |old value|) × 100. A positive result indicates an increase; a negative result indicates a decrease. For example, a price that goes from $80 to $100 is a 25% increase. Use Panel 3 of this calculator.
Percentage change measures the change from a starting value to a new value and has a direction (increase or decrease). Percentage difference measures how different two values are from each other symmetrically, using their average as the denominator: |A - B| / ((A + B) / 2) × 100. It is useful when neither value is a clear 'before' or 'after'.
To add a percentage: result = original × (1 + percent/100). To subtract: result = original × (1 - percent/100). For example, adding 20% to $50: $50 × 1.20 = $60. Subtracting 20% from $50: $50 × 0.80 = $40. Use Panel 5 of this calculator for this type of calculation.
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