Percentage Calculator

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.

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.

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.

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.

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.

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.

Results are displayed to four decimal places. For everyday values like tips, discounts, test scores, and tax rates, that is more precision than you normally need. Very large values near JavaScript's floating-point limits can show minor rounding drift.