The number that matters
Risk to reward on its own says nothing. 1:5 is a losing strategy at a 10% win rate and 1:0.5 is a winning one at 80%. The pair of numbers is the strategy; either one alone is marketing.
The break-even win rate is where they meet:
break-even win rate = 1 ÷ (1 + R)
At 1:1 you need 50%. At 1:2, 33.3%. At 1:3, 25%. Anything above that line makes money over enough trades; anything below it loses, no matter how good each individual trade felt.
Expectancy
expectancy = (win rate × R) − (loss rate × 1), in units of risk.
0.35R per trade means that on average, every trade you take is worth about a third of what you risk. Risk R500 a trade and that is R175 a trade, R17 500 over a hundred trades — as an average, with losing streaks along the way that feel nothing like an average.
Costs are not a rounding error
Spread and commission come off every trade, win or lose. On a 20 pip scalp a 2 pip spread is 10% of the trade before it starts, which is the difference between an edge and a hobby. Put your real cost in the field and watch the break-even win rate move.
Use your own win rate
The honest input here is what you have actually done, not what you hope to do. TradeLens works it out from your closed trades and shows it next to your discipline score, so the number in this box can be a fact instead of a feeling.