Calculator 1
What is X% of Y?
What is
% of
?
0
200 × 15 / 100 = 30
Calculator 2
X is what % of Y?
is what % of
?
0%
30 / 200 × 100 = 15%
Calculator 3
Percentage Change
From
to
+20%
(120-100)/100 × 100 = +20%
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Percentage Formulas Explained
How do I calculate what X% of Y is?+
Multiply Y by X and divide by 100. Formula: Result = Y × X / 100. Example: What is 15% of 200? → 200 × 15 / 100 = 30. Use Calculator 1 above for instant results.
How do I find what percentage one number is of another?+
Divide X by Y and multiply by 100. Formula: Percentage = (X / Y) × 100. Example: 30 is what percent of 200? → (30 / 200) × 100 = 15%. Use Calculator 2 above.
How do I calculate percentage increase or decrease?+
Formula: % Change = ((New Value - Old Value) / Old Value) × 100. A positive result is an increase, negative is a decrease. Example: Price went from $100 to $120 → ((120-100)/100) × 100 = +20% increase. Use Calculator 3 above.
How do I calculate a tip as a percentage?+
Use Calculator 1: "What is 20% of 85?" → 85 × 20 / 100 = $17 tip. For a 15% tip on $50: 50 × 15 / 100 = $7.50. A quick mental trick for 20%: divide by 10, then double. $85 / 10 = $8.50, × 2 = $17.
How do I calculate a discount?+
To find the sale price after a discount: Sale Price = Original Price × (1 - Discount%/100). Example: 30% off $80 → 80 × (1 - 0.30) = 80 × 0.70 = $56. Or use Calculator 1: "What is 30% of 80?" = $24 discount, then $80 - $24 = $56.
How do I add a percentage to a number?+
Formula: Result = Number × (1 + Percentage/100). Example: Add 20% to $50 → 50 × 1.20 = $60. This is used for calculating prices with sales tax, or salaries with a raise. For a 7% sales tax on $45: 45 × 1.07 = $48.15.