Risk of Ruin Calculator
Estimate the probability a fixed-fractional trading strategy blows past a ruin threshold, from your win rate, payoff ratio and risk per trade.
Enter your win rate, payoff ratio and the fraction of equity you risk per trade. A fixed seed runs 10,000 hypothetical accounts to estimate how often that plan drops past your ruin threshold.填入胜率、盈亏比与每笔交易承担的资金比例。程序以固定随机种子模拟 10,000 个假想账户，估算该策略跌破你设定的爆仓线的频率。
Fill in win rate, payoff and risk to estimate the odds.填入胜率、盈亏比与风险即可估算爆仓概率。
- Expectancy / trade每笔期望
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- Ruin threshold爆仓线
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- Accounts simulated模拟账户数
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- Trades per run每次笔数
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Risk of ruin is the probability that a fixed-fractional strategy — one that risks a set percent of current equity on each trade — drops past a drawdown you define as ruin before its edge can compound. It depends on three things: how often you win, how much a win pays relative to a loss, and how much you stake each time. The first two set your edge; the third decides whether that edge survives its own volatility.爆仓概率是指一个固定比例策略（即每笔交易都按当前资金的固定百分比下注）在其优势还来不及复利之前，就跌破你所定义的爆仓回撤的概率。它取决于三点：赢的频率、一次盈利相对一次亏损的倍数，以及每次下注的大小。前两者决定你的优势，第三者则决定这份优势能否熬过它自身的波动。
01How it is estimated如何估算
Ruined if equity ever ≤ 1 − dd (starting equity = 1)若资金曾 ≤ 1 − dd 则爆仓（起始资金 = 1）
Risk of ruin = ruined accounts ÷ 10,000 × 100%爆仓概率 = 爆仓账户数 ÷ 10,000 × 100%
Expectancy (R) = W·b − (1 − W)每笔期望（R） = W·b − (1 − W)
There is no tidy closed form for a compounding, fixed-fractional account, so this runs a Monte-Carlo: 10,000 simulated accounts, each trading the plan for the number of trades you set, counting how many ever cross the ruin line. A fixed random seed makes the answer reproducible — the same inputs always return the same number, so you can compare plans honestly rather than chase a shifting figure.对于一个复利的固定比例账户，并没有简洁的闭式解，因此这里采用蒙特卡洛模拟：10,000 个模拟账户，每个都按你设定的笔数交易该策略，统计有多少个曾越过爆仓线。固定的随机种子让结果可复现——相同输入始终返回相同数字，你可以据此诚实地比较不同方案，而非追逐一个飘忽的数值。
02A worked example一个算例
Suppose a trader wins 50% of the time at a 1 : 1 payoff and risks 2% of equity per trade, calling a 50% drawdown ruin, over 500 trades.假设一位交易者胜率为 50%、盈亏比为 1 : 1，每笔风险为资金的 2%，将 50% 回撤视为爆仓，共交易 500 笔。
- Expectancy = 0.5 × 1 − 0.5 = 0.00 R — a coin flip, no edge.期望 = 0.5 × 1 − 0.5 = 0.00 R——一枚硬币，毫无优势。
- With no edge, ruin is driven purely by the size of the swings. The simulation returns roughly 16% risk of ruin at this stake.在没有优势时，爆仓完全由波动幅度决定。在此下注比例下，模拟返回约 16% 的爆仓概率。
- Cut the stake to 1% and the same edgeless plan falls to a low single-digit chance of ruin — the payoff never changed, only the bet size.将下注比例降到 1%，同样毫无优势的策略，其爆仓概率便降至低个位数——盈亏比从未改变，改变的只是下注大小。
That is the whole lesson in one line: a break-even strategy can still ruin you if you bet too much, and it can survive almost indefinitely if you bet a little. Position size, not the payoff, is doing the heavy lifting.这就是全部道理，浓缩成一句：一个不赚不赔的策略，若下注过重，仍可能让你爆仓；若下注轻微，则几乎能无限期存活。真正起决定作用的是仓位大小，而非盈亏比。
03The common trap常见陷阱
It is tempting to think a positive expectancy makes ruin impossible. It does not. An edge that pays off on average still arrives as a jagged string of wins and losses, and a long-enough cold streak at a large stake can carry equity below the ruin line before the average ever asserts itself. Doubling your risk per trade does not double your return — it multiplies the depth of your drawdowns and can push a perfectly profitable plan into the ruin zone.人们很容易以为正期望就能杜绝爆仓。并非如此。一份平均盈利的优势，实际是以盈亏交错的锯齿状序列到来的；足够长的连亏叠加较大的下注，可能在平均值显现之前就把资金拖到爆仓线以下。把每笔风险翻倍并不会让收益翻倍——它会成倍加深你的回撤，足以把一个本该盈利的策略推入爆仓区间。
04Where this breaks它的局限
This is a clean model of one idealized plan. Real trading is messier, and the estimate should be read with a few honest limits in mind:这是对一个理想化策略的简洁建模。真实交易要复杂得多，读取这个估算时应记住几点诚实的局限：
- Every trade is treated as independent and identical. Real win rates and payoffs drift with the regime; a plan that worked in a trend can bleed in a chop. The model assumes the odds you type stay fixed forever.每笔交易都被视为独立且相同。真实的胜率与盈亏比会随市场环境漂移；在趋势中奏效的策略，在震荡里可能持续失血。模型假设你输入的赔率永远固定不变。
- Wins and losses are fixed at exactly b and 1. Actual outcomes scatter — a rare outsized loss (a gap through your stop) is not captured, so true ruin risk can be higher than the clean figure.盈亏被固定为恰好 b 和 1。真实结果是分散的——一次罕见的巨亏（跳空穿过止损）并未被纳入，因此真实的爆仓风险可能高于这个干净的数字。
- Ruin is a threshold you chose. Crossing a 50% drawdown on paper is not a margin call, and stopping short of it is not safety. Treat the percent as a planning line, not a verdict.爆仓线是你自己选定的。纸面上跌破 50% 回撤并不等于被强平，而没跌到它也不等于安全。请把这个百分比当作一条规划线，而非最终裁决。
Your edge decides whether you win in the long run; your bet size decides whether you are still around to see it. Smaller risk per trade slashes the odds of ruin far faster than it dents your returns.你的优势决定长期能否盈利；你的下注大小决定你是否还活着看到那一天。降低每笔风险，削减爆仓概率的速度，远快于它对收益的损耗。
Ground the bet-size half in the lesson on 在这节课中夯实下注大小这一半 position sizing仓位管理, or turn your win rate and payoff into an edge with the ，或用 risk-to-reward calculator盈亏比计算器.将你的胜率与盈亏比换算成优势。