Break-even win rate
The win rate at which a given risk-reward ratio neither makes nor loses money, before costs.
In plain English
It equals 1 ÷ (1 + reward-to-risk). Costs push the real break-even rate higher, which matters most on small targets.
Example
At a 1:2 ratio the break-even win rate is 1 ÷ 3, about 33%. At 1:1 it is 50%.