Percentages come up constantly — tips, taxes, sales, and grades. This calculator handles the everyday cases: finding a percent of a number, or increasing and decreasing a number by a percent.
The three operations
“% of” multiplies the number by the percent over 100. “Increase by %” adds that amount on top; “decrease by %” takes it away. To compare two numbers as a percentage change instead, use the dedicated percentage change calculator.
A worked example
To find 20% of 50, multiply 50 by 0.20 to get 10. To increase 50 by 20%, add that 10 for 60; to decrease it, subtract for 40. The same percentage produces three different answers depending on what you're actually asking, which is why choosing the right operation matters as much as the numbers.
Everyday percentage shortcuts
A few tricks make this quick in your head. Percentages are reversible: 20% of 50 equals 50% of 20 — both are 10 — so flip the problem whenever one side is rounder. To take 10% of any number, move the decimal one place left; 5% is simply half of that, and 15% is 10% plus 5%.
For tips, taxes, and discounts these shortcuts add up fast. And when you need to compare two numbers rather than adjust one — say, how much a value grew — reach for the percentage change calculator instead.