The 2% Rule vs. Actual Ruin Probability

The Origin of the 2% Rule

The 2% rule states: never risk more than 2% of your account on a single trade. It was popularized by Alexander Elder in *Trading for a Living* (Wiley, 1993) and is one of the most widely repeated rules in trading education. It's a reasonable starting point — but it is not universally optimal.

When 2% Is Too Much

For a strategy with:

• 40% win rate
• 1:1.5 R-multiple
• 40 trades per month

At 2% risk per trade, Monte Carlo simulation reveals a 15–25% probability of ruin over a 6-month period. Dropping to 1% reduces that probability to under 5%. According to Perry Kaufman in *Trading Systems and Methods* (Wiley, 2019, 6th edition), "position sizing rules must be calibrated to the specific strategy — a universal percentage is a convenience, not a solution."

When 2% Is Too Conservative

For a strategy with:

• 60% win rate
• 1:2 R-multiple
• 10 trades per month

At 2% risk, ruin probability is under 1% over 12 months. This suggests there's room to size up to 3% or even 4% while maintaining survival probability above 95%.

A Better Approach

Instead of following a fixed rule:

1. Define your win rate and average R-multiple from at least 100 trades of data

2. Set your maximum acceptable drawdown (your real ruin threshold)

3. Run Monte Carlo simulation at different risk levels (1%, 2%, 3%, 5%)

4. Identify the risk level where survival probability exceeds 90–95%

This highlights a position size tailored to your strategy, not a one-size-fits-all number.

Explore Your Risk Levels

The Risk of Ruin Calculator lets you test different risk percentages. RangeSight adds real volatility data for deeper analysis.

Conceptually this provides a framework. In practice, outcomes vary across simulations. Testing multiple scenarios reveals how consistent a strategy actually is.