How to Use Monte Carlo Simulations for Smarter Trading Decisions

What is a Monte Carlo simulation?

A Monte Carlo simulation is a computational technique that uses repeated random sampling to model the probability of different outcomes in a process that is inherently uncertain. Named after the famous casino district in Monaco, the method was developed in the 1940s by scientists working on nuclear weapons projects who needed to model complex systems with many random variables.

The core idea is elegant: instead of trying to solve a complex probability problem analytically (which is often impossible), you simulate the process thousands or millions of times, each time using random inputs drawn from known probability distributions. The aggregate of all those simulations gives you a statistical picture of what is likely to happen, what could happen in the best case, and what could happen in the worst case.

Monte Carlo methods are used across finance, engineering, physics, and artificial intelligence. In sports investing, they are one of the most powerful tools available for understanding risk, sizing positions, and setting realistic expectations for your portfolio trajectory.

How Monte Carlo applies to trading

Sports investing outcomes are probabilistic. Even if you have a genuine edge — say, a 54% win rate on -110 positions — you cannot predict the sequence of wins and losses you will experience. Two investors with identical edges will have wildly different short-term results depending on the random order of their outcomes.

This is where Monte Carlo simulation becomes invaluable. Instead of asking "what will my results be?", you ask "what are all the things my results could be?" By simulating your exact trading strategy — your edge, your allocation size, your number of positions — across thousands of randomized sequences, you build a distribution of possible outcomes that reveals the true range of what to expect.

The inputs to a trading Monte Carlo simulation are straightforward:

• Starting portfolio — how much capital you begin with
• Estimated edge per position — your average expected value, often derived from your CLV or model-based edge
• Average returns — the typical decimal returns of your positions
• Position sizing method — flat allocation, percentage of portfolio, or Kelly criterion
• Number of positions — how many positions per simulation run (e.g., a season of 500 positions)
• Number of simulations — how many parallel "futures" to generate (typically 1,000–5,000)

A worked example: 1,000 simulated seasons

Let's say you have a starting portfolio of $10,000, an estimated 3% edge per position, average returns of 2.00, flat allocations of 2% of initial portfolio ($200 per position), and you plan to place 400 positions over a season. Running 1,000 simulated seasons produces a distribution of final portfolio values.

In a typical simulation with these parameters, you might see results like:

These numbers tell a story that no single-point estimate can. Yes, your expected profit is positive, but there is a 17% chance you finish the season at a loss despite having a real edge. There is an 18% chance you experience a drawdown of 20% or more at some point during the season. And the spread between the best and worst outcomes is enormous — from 76% growth to 28% loss.

This is the reality of trading that many people underestimate. An edge does not guarantee short-term profit. Monte Carlo simulation makes this viscerally clear by showing you the full range of what could happen.

Interpreting probability distributions

The output of a Monte Carlo simulation is not a single number — it is a distribution. Understanding how to read this distribution is critical.

Key metrics to extract from the distribution:

• Median outcome: The 50th percentile of final portfolios. This is a more robust estimate of your "typical" result than the mean, because it is less influenced by extreme outliers.
• Confidence intervals: The range between, say, the 10th and 90th percentiles tells you that 80% of simulated outcomes fall within this band. This is your realistic planning range.
• Probability of profit: What percentage of simulations end above your starting portfolio. Even with a genuine edge, this is rarely 100% over short time horizons.
• Maximum drawdown distribution: How deep could your worst losing streak get? This is crucial for psychological preparation and portfolio sizing.
• Risk of ruin: The probability of your portfolio hitting zero (or a critical threshold). This should be kept below 1–2% for any responsible trading strategy.

Risk of ruin analysis

Risk of ruin is one of the most important outputs of a Monte Carlo simulation. It answers the existential question: "What is the probability that I go completely broke?"

Risk of ruin depends on three interacting factors:

• Edge size: A larger edge reduces ruin probability exponentially. Moving from a 1% edge to a 3% edge can reduce risk of ruin from 15% to under 1%.
• Position sizing: Larger positions relative to portfolio dramatically increase ruin risk. An investor staking 10% of portfolio per position faces far more ruin risk than one staking 2%, even with the same edge. This is why the Sharpe ratio matters — it measures return relative to risk.
• Portfolio depth: A larger starting portfolio (in terms of position units) provides more cushion to absorb losing streaks. As explored in our variance and portfolio simulation guide, the relationship between portfolio size and survivability is non-linear.

A well-calibrated Monte Carlo simulation lets you dial in your position sizing to keep risk of ruin at an acceptable level. For most serious investors, the target is under 2%. This often means trading 1–3% of your portfolio per position, depending on your edge and the returns you typically play.

How Yoseri runs up to 5,000 scenarios

Yoseri's simulation engine generates up to 5,000 randomized scenarios based on your actual trading history and parameters. This is not a toy calculator — it uses your real data to produce meaningful projections.

Here is how it works:

• Historical calibration: The simulator pulls your actual win rate, average returns, CLV, and position sizing pattern from your tracked positions. This means the simulation reflects your real strategy, not a hypothetical one.
• Forward projection: Using those calibrated parameters, the engine simulates your next N positions across 5,000 independent sequences. Each sequence is a different possible future where your edge plays out against a different random ordering of outcomes.
• Distribution output: The results are aggregated into percentile bands (10th, 25th, 50th, 75th, 90th) that show the realistic range of where your portfolio could end up.
• Risk metrics: Maximum drawdown distribution, risk of ruin at various thresholds, and probability of reaching specific profit targets are all calculated from the simulation output.

Why 5,000 scenarios and not 500 or 50,000? At 5,000 simulations, the statistical estimates of key metrics (median, percentiles, risk of ruin) stabilize to within about 1% accuracy. Going higher adds marginal precision at significant computational cost. Going lower risks noisy estimates, particularly for tail events like risk of ruin where you need many simulations to capture rare outcomes reliably.

Practical use cases

Portfolio sizing

How large does your portfolio need to be? Monte Carlo answers this directly. Run simulations with different starting portfolios until you find the amount that keeps risk of ruin below your tolerance. If you plan to allocate $200 per position, you might discover that a $5,000 portfolio carries 8% ruin risk while a $10,000 portfolio reduces it to under 1%.

Position sizing optimization

Should you invest 1%, 2%, or 3% of your portfolio? Monte Carlo shows the tradeoff. Higher allocations mean faster portfolio growth in the median case but wider distributions and higher ruin risk. Lower allocations mean slower growth but much more stability. The Monte Carlo simulation guide demonstrates this tradeoff in detail.

Season projections

Before a new season starts, run a simulation with your expected number of positions, estimated edge, and current portfolio. The resulting distribution gives you a realistic range of outcomes to plan around. If the 10th percentile scenario is not acceptable to you, you need to either reduce your position sizing, increase your portfolio, or improve your edge before starting.

Strategy comparison

Monte Carlo simulation lets you compare two strategies side by side. For example, flat allocation at 2% of initial portfolio versus Kelly criterion at quarter-Kelly. By running both through the same 5,000 simulated sequences, you can see exactly how the distributions differ in terms of expected growth, risk, and worst-case outcomes.

Drawdown preparation

The simulation reveals the most likely maximum drawdown you will face. If 80% of simulated seasons include a drawdown of at least 15%, you know to expect it and prepare psychologically. Drawdowns are inevitable — Monte Carlo tells you how deep they are likely to go so you are not caught off guard.

Limitations and honest expectations

Monte Carlo simulations are powerful, but they are only as good as their inputs. If your estimated edge is wrong (which it often is, especially for newer investors), the entire distribution shifts. A simulation showing 85% probability of profit assumes your 3% edge is real — if your actual edge is 1%, the picture changes dramatically.

This is why Yoseri calibrates simulations from your actual tracked performance rather than requiring you to guess your edge. Your CLV history, as discussed in our simulation methodology article, provides the most reliable estimate of your true edge, and using it as the simulation input produces the most realistic projections.