There is no set formula for determining this. That is why overclocking has strict warnings that doing it may cause your computer to quit working.

In most cases the computer will reach a state of instability before anything happens and you must return it to more stable settings....

If this is going to be something that you are going to experiment with...google for overclocking that specific chip and the best procedures for attempting....This is important because some chips are locked and cannot be overclocked....trying to will damage the chip severely