If you want to get an insight into the way your brain works, you can use this calculator. This calculator can also help you to calculate your balance ability. Please read the following before using the calculator:

Stand at a location away from all objects
Ask a friend, so that he/she can stand near by you to help you in case of unbalancing
Close your eyes
Stand on one leg, and calculate the time

You can use a stop watch to get the accurate time.