Module 1 — Risk in numbers · Lesson 3 of 10 · 6 min
Losing streaks and risk of ruin: how many to expect
The real odds of five, eight or ten losses in a row, and how risk per trade changes the chance of disaster.
Almost everyone underestimates losing streaks. After three stops in a row we think "something's wrong". After five we're convinced the system is broken. Yet the maths says losing streaks are normal: they aren't a sign of a mistake, they're a property of chance. Knowing the numbers helps you stay calm when they arrive.
How likely is a losing streak?
If each trade is independent with a win probability p, the chance that the next k trades all lose is (1 − p) to the power of k. But the question that really matters is a different one: over a given number of trades, how likely are you to meet a streak of k losses in a row at least once? Over 100 trades:
| Win rate | ≥5 losses in a row | ≥8 | ≥10 |
|---|---|---|---|
| 40% | 98% | 49% | 21% |
| 50% | 81% | 17% | 4.4% |
| 60% | 46% | 3.6% | 0.6% |
Take your time with these. Even a trader who wins 60% of the time has nearly a one-in-two chance of seeing five stops in a row in the next 100 trades. With a 40% win rate (perfectly normal for systems with a high reward-to-risk ratio), a run of eight losses turns up about once in every two sets of 100 trades, and a run of ten about once in five. (The figures come from an exact calculation assuming independent trades. In real markets there are stretches that favour your method and stretches that don't, so streaks can run longer.)
What a losing streak does to your account
A run of losses doesn't wear down your balance in a straight line, because each loss is a percentage of what's left:
| Risk per trade | After 5 losses | After 10 | After 20 |
|---|---|---|---|
| 1% | −4.9% | −9.6% | −18.2% |
| 2% | −9.6% | −18.3% | −33.2% |
| 5% | −22.6% | −40.1% | −64.2% |
| 10% | −41.0% | −65.1% | −87.8% |
At 1% risk, ten losses in a row cost less than 10%: a bad patch, but the account is still standing. At 5%, the same ten losses take 40% off and you'd need almost +67% to recover. Position size is the most powerful lever you have over your own fate.
Risk of ruin
Risk of ruin is the probability of losing so much of your account that you can't keep playing. It depends on three things: the risk per trade, the system's statistical edge (win rate and reward-to-risk ratio) and the number of trades.
A teaching simulation. A system with a 45% win rate and a 1:2 reward-to-risk ratio (so an expectancy of +0.35R per trade, a rather nice assumption). We run 20,000 paths of 500 trades and count how many hit a 50% drawdown at any point:
| Risk per trade | Paths that hit −50% |
|---|---|
| 1% | almost none |
| 2% | almost none |
| 5% | about 1.5% |
| 10% | about 16% |
Even with a good system, risking 10% per trade sends more than one path in six down to half its capital. And what if the system has no edge? With a 40% win rate and a 1:1 ratio (expectancy −0.2R) the simulation shows about 95% of paths hitting −50% even at 1% risk: no amount of risk management turns a losing system into a winning one. It can only buy time.
The exact figures depend on the assumptions (it's a simulation, not a forecast); the message holds up: risk per trade is what separates a system with an edge that survives from one that destroys itself.
What to do when the streak arrives
- Check you followed your rules. If you did, the losses are the cost of doing business. If you didn't, the problem is your execution, not the system.
- Don't change the system mid-streak. With so little data you can't tell whether it works.
- Apply your written limits (see the drawdown lesson): cut the risk or stop.
- Record your state of mind. After five losses the biggest danger isn't the market, it's emotional: the urge to win it back.
When it really is the system
The difference shows in the numbers: if your current drawdown is well beyond the maximum you saw in backtest and demo (say one and a half or two times as deep), or the stats of your last 50-100 trades are far from what you expected, then it makes sense to question the system. A short streak isn't enough to convict it.
In short
- Losing streaks are normal: even at 60% wins, five stops in a row over 100 trades happen almost half the time.
- A streak hits your account in proportion to your risk per trade: 10 losses cost −9.6% at 1% risk and −40% at 5%.
- Risk of ruin climbs fast with risk per trade, even for systems with an edge.
- No risk management can rescue a system with no edge.
Practice
- In a spreadsheet, simulate 200 trades with a 45% win probability and 1:2 reward-to-risk (use a random function). Note the longest losing streak. Repeat five times.
- Work out the effect of 8 losses in a row at 1%, 2% and 3% risk.
- Write down what you'll do at the third, fifth and eighth consecutive stop.
Test what you've learned
1. At a 60% win rate, how likely are at least 5 losses in a row over 100 trades?
2. 10 losses in a row at 5% risk per trade cost about?
3. Can risk management save a system with no statistical edge?
4. After 4 stops in a row, your first step is?
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Educational content, not financial advice. Trading involves risk.