Risk of ruin is the probability that a string of losses wipes out your account before your edge can pay off. Even a profitable method can blow up if you risk too much per trade, because losing streaks are inevitable. This is why the small, fixed risk-per-trade rule exists. Sizing, not setups, decides survival.
What risk of ruin is
Risk of ruin is the probability that you lose so much your account cannot recover, practically that you blow up, before your edge has time to work. It depends on three things: your edge (expectancy), your risk per trade, and the reality of losing streaks.
The uncomfortable truth it reveals is that a positive expectancy is not enough. If you size too large, a normal run of losses can end you before the average ever plays out.
Losing streaks are inevitable
Even a method that wins most of the time will string losses together. With a 50% win rate, runs of five, six or seven losses in a row happen routinely over a long enough sample. That is how randomness works. It is not a sign the method is broken.
The question is not whether you will hit a losing streak. It is whether your account survives it. That is decided entirely by how much you risked on each trade.
Why the small risk rule exists
This is the maths behind the classic rule of risking a small, fixed percentage of your account per trade, often around 1%. Risk 1% and a ten-loss streak costs you roughly 10%. That is painful but survivable, and it can be recovered. Risk 10% per trade and the same streak wipes you out.
Size is an output of your risk rule and your stop distance. It is never an input you pick because you feel confident. A position-size calculator turns your risk cap and stop into the correct size automatically.
Position sizing is survival
Most traders get the hierarchy backwards. Finding setups is the fun part, and everyone obsesses over it. But position sizing is what keeps you in the game long enough for any edge to matter. It is the least glamorous skill in trading.
You cannot control whether the next trade wins. You can completely control how much it costs you if it loses. Get the sizing right and even a rough patch is survivable. Get it wrong and even a good method can end your account.
That is why, on this site, risk comes before reward, always. This is education, not advice.
Questions
Can a profitable strategy still blow up an account?
Yes. A method with positive expectancy can blow up if you risk too much per trade. A normal run of losses can end an over-sized account before the average plays out.
Why risk only 1% per trade?
It keeps losing streaks survivable. At 1%, a ten-loss streak costs about 10%. At 10% per trade, the same streak wipes you out.
Are losing streaks normal?
Completely. Runs of five, six or seven losses happen routinely over a long sample. A streak is not proof a method is broken.
What is the most important skill in trading?
Position sizing. You cannot control whether a trade wins, but you can control what it costs if it loses. Sizing keeps you in the game long enough for any edge to matter.
What does risk of ruin depend on?
Three things: your expectancy, your risk per trade, and the inevitability of losing streaks.
70–80% of retail investor accounts lose money trading CFDs. This page is education, not advice. All trade examples are constructed composites.
