Math
Percentage Calculator
Solve all three percentage questions: X percent of Y, X is what percent of Y, and percent change. Step-by-step, instant.
Pick a question
Result
30
15% of 200 = 30
Multiply 200 by 0.15 (which is 15 percent expressed as a decimal).
Frequently Asked Questions about the Percentage Calculator
How do I calculate a percentage?
Multiply the total by the percent written as a decimal. For 20% of 50: 0.20 x 50 = 10. This calculator covers all three common setups (X% of Y, X is what % of Y, and percent change from X to Y), so you pick the mode that matches your question.
What is 20% of 100?
20% of 100 is 20. The formula is (20 / 100) x 100 = 20. Enter 20 in the percent field and 100 in the value field under "X% of Y" to confirm.
How do I find percent change?
Subtract the old value from the new value, divide by the absolute value of the old value, then multiply by 100. A positive result is an increase; a negative result is a decrease. For example, a price that moves from $80 to $100 is a 25% increase: (100 - 80) / 80 x 100 = 25.
What is the difference between percentage and percent?
They refer to the same concept. Percent (symbol %) is the unit meaning "per hundred", and percentage is the general term for a value expressed in those units. Saying "50 percent" and "50%" means exactly the same thing, half of the whole.
How do I calculate a tip without this calculator?
To get 20%, shift the decimal one place left to find 10%, then double it. On a $48.50 check: 10% is $4.85, so 20% is $9.70. For 15%, find 10%, halve it to get 5%, then add the two together.
How do I calculate the original price before a discount?
Divide the sale price by (1 minus the discount as a decimal). If you paid $40 after a 20% discount: 40 / (1 - 0.20) = 40 / 0.80 = $50. You can also use the "X is what % of Y" mode to verify: 40 is 80% of 50.
How accurate is this calculator?
Results are rounded to six decimal places. For everyday values like tips, discounts, test scores, and tax rates, the output is precise. Very large numbers near the limits of JavaScript's 64-bit floating point (roughly 15 significant digits) can show minor rounding drift, but nothing you would encounter in normal use.