There are 2 basic elements to constituting the Kelly criterion: (Here I am talking in the direction of trading for ease)

1. WIN ratio (W): probability of you winning in total trade
2. Reward:Risk ratio (R): profit pips / loss pips

Kelly% = W – [(1-W)/R]

Two important parameters: W greater than or equal to 0.5 and R greater than or equal to 1

If W is less than or equal to 0/5, the ratio R must be high, R greater than or equal to 1 to compensate.