What it measures
Risk/reward ratio (RR) compares how much you can win on a trade versus how much you risk. A 2:1 RR means the take-profit is twice as far from entry as the stop-loss — you risk 1 unit to make 2.
Why it interacts with win rate
RR and win rate are not independent. A strategy with 2:1 RR only needs to win 34% of trades to break even (before spread/commission). A 1:1 strategy needs 50%+. Most EA marketing leads with win rate; always check both together.
Common pitfalls
Do not widen the take-profit to improve the RR after entry — that changes the original thesis. The RR declared before entry is the only honest one. Post-hoc adjustments are a form of optimism bias, not strategy.