I believe what you're talking about here is risk vs. reward in poker, and how to turn a direct odds ratio into a breakeven point in % terms. For example, there's $2 in the pot, my opponent bets $1, and I have to call $1 for the chance to win $3 total. Hence my direct odds are 3 : 1.
The equation is breakeven point = risk / (risk + reward), so it is simply 1 / (1 + 3) = 1 / 4 = 0.25 or 25% in this example. If we win the pot 25% of the time, 25% of the time we win $3, 75% of the time we lose $1. Longrun we break even.
Hope that helps. PM me for coaching!