The easiest way to calculate a percentage is taking 10 percent of any number and multiplying it to find the percentage desired. To calculate 10 percent of a number, simply move the decimal point one place to the left.
If there is no decimal point, put a decimal point between the last and the second-to-last digit. To calculate 20 percent, simply multiply 10 percent by 2.
A percentage is a representation of a fraction. It is easy to calculate certain percentages by remembering their fractional representation. For example, 50 percent is equal to one-half; thus dividing a number by two yields 50 percent of that number. Twenty-five percent is equal to one-quarter of a number; thus dividing a number by four gives 25 percent of the number.