The Kelly's formula is aimed at finding the optimal value for a bet, basing on its related odd. Such optimal value is represented by a percentage of the total budget and it is obtained as a half-way between a too high risk and a too lower income.
In order to calculate the Kelly's formula, it is necessary to know:
The recommended value to bet [I] is calculated as follows:
I = [(Q x P/100 - 1) / (Q-1)] x B
Recommended value to be bet on 1: I = [(1.98 x 65/100 - 1) / (1.98-1)] x 200 = 58.87€
In order to mitigate the possibility of budget loss (caused by wrong estimatation of the probability of success), there is a more "conservative" variant, called Kelly/2. This method considers to bet only helf of the obtained value form the formula, i.e. I/2.