Percentages are a part of a whole. You can display percentages in several ways, such as 0.1 percent, 0.001 in decimal form or 1/1,000 in fraction form. The easiest way to calculate the percentage of a number is to convert the percentage into decimal form. This calculation requires only that you understand basic math. You will see percentages in a lot in business and tax situations, in which you will need to determine payments based on percentage.

Find the number you want to find 0.1 percent of. For example, a person wants to know 0.1 percent of $40.

Convert 0.1 percent to decimal form; 0.1 percent is the same as 0.001.

Multiply the decimal form of 0.1 percent by the number you want to find 0.1 percent of. In the example, 0.001 times $40 equals 0.04, or 4 cents.