Risk of Ruin Basics: Why Position Size Beats Predictions

Risk of ruin is the probability that your account drops to a level where recovery is unlikely. It does not matter how good your strategy is if you size too large. Most blown accounts are not caused by bad predictions; they are caused by oversized risk.

The simple idea

The larger your risk per trade, the fewer losses it takes to damage your account. Even a strategy with a decent win rate can collapse if the drawdown is too large.

Why smaller size wins long term

• Smaller risk keeps you in the game during losing streaks.
• It reduces emotional swings and improves decision making.
• It allows time for the edge to play out over many trades.

A practical rule

Risk 0.5% to 1% per trade until you have a large sample size. If you cannot stay disciplined at 1%, you will not survive at 3%.

Combine with process

Risk control works best when paired with process: a checklist, a consistent session, and a single setup. That combination dramatically lowers the chance of ruin and increases the chance of long-term improvement.

In trading, survival is the first edge. If you protect your downside, your upside has room to grow.