🧮 Math 3 modes Last tested2026-05-13
Percentage made stupid easy.
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Quick answer
15% of 200 = 30. Three modes in one calculator: percent of a number, what % a number is of another, and the % change between two numbers.
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Percentage Calculator
What is
%
of?15% of 200
30
✨ Live · Three percentage modes in one tool
🧮 The 3 formulas
Three modes. Three formulas.
Mode 1: X% of Y
result = (X / 100) × Y
e.g. 15% of 200 → (15/100) × 200 = 30
Mode 2: X is % of Y
result = (X / Y) × 100
e.g. 30 of 120 → (30/120) × 100 = 25%
Mode 3: % Change
result = ((Y − X) / |X|) × 100
e.g. 100 to 150 → ((150−100)/100) × 100 = +50%
❓ FAQ
Common questions.
How do I find a percentage of a number?
Multiply the percentage (as a decimal) by the number. For example, 15% of 200 = 0.15 × 200 = 30.
How do I find what percent one number is of another?
Divide the part by the whole, then multiply by 100. For example, 30 out of 120 = (30 ÷ 120) × 100 = 25%.
How do I calculate percentage change?
Subtract the old value from the new, divide by the old value, multiply by 100. From 100 to 150: ((150 − 100) ÷ 100) × 100 = 50% increase.
Whats the difference between percentage points and percent?
Percentage points are a direct subtraction. Going from 5% to 8% is +3 percentage points, but a 60% relative increase. The distinction matters when discussing rates.
How do I reverse-engineer a percentage?
If 20 is 25% of some number, that number = 20 ÷ 0.25 = 80. Divide the part by the percentage (as a decimal) to find the whole.