It is a tool that lets you do a simple calculation: how many percent of X is Y? The tool is pretty straightforward. All you need to do is fill in two fields and the third one will be calculated for you. Other than being helpful with learning percentages and fractions, this tool is handy in many different situations. For example, you may calculate an amount of income tax. That is pretty much all you need to know. Keep reading if you would like to know a little more.