What is Risk of Ruin and How Do I Calculate It?

What you will find out: What risk of ruin actually means, why a profitable strategy can still blow your account, and how to find your own ruin probability before trading live.

What is Risk of Ruin?

Risk of ruin is the probability that your account loses so much money it can’t realistically recover. In Edge Engine, ruin is defined as losing 80% or more of your starting balance.

A strategy can have positive expectancy and still carry meaningful ruin risk. It makes money on average, but that doesn’t guarantee survival. Expectancy tells you the long-run average. Risk of ruin tells you the chance you never get there.

Why Positive Expectancy Isn’t Enough

Imagine flipping a coin where heads pays you $2 and tails costs you $1. The expectancy is clearly positive. You make $0.50 per flip on average. Over thousands of flips you’ll come out ahead.

But what if you only have $5 and you’re betting $1 per flip? A short run of tails, which is completely normal, wipes you out before the edge has time to work. The strategy was profitable. You just didn’t survive long enough to see it.

This is exactly what happens to traders. The edge is real, the math works, but the sizing relative to the account doesn’t leave enough room for normal losing streaks. Risk of ruin quantifies that danger.

What Drives Ruin Risk

Three things determine how likely you are to hit ruin:

Win rate and R-multiples. A stronger edge (higher expectancy) naturally lowers ruin risk because the account recovers faster from drawdowns. But even strong edges carry ruin risk if the other two factors are wrong.

Risk per trade as a percentage of your account. This is the biggest lever. Risking 1% of your account per trade and risking 5% per trade with the same strategy produce dramatically different ruin probabilities. The edge is identical. The survival rate is not.

Number of trades. More trades means more opportunities for unlucky streaks. A strategy with low ruin risk over 100 trades might show meaningful ruin risk over 1,000 trades, simply because longer sequences have more chances to produce extreme losing runs.

Why You Can’t Just Calculate It on Paper

There are closed-form formulas for risk of ruin, but they make simplifying assumptions that don’t hold in real trading. They assume fixed bet sizes, perfectly independent outcomes, and symmetrical distributions. Real trading has none of those things.

Monte Carlo simulation gives you a much more honest answer. It runs thousands of randomized trade sequences using your actual stats and counts how many of them hit ruin. No assumptions about distribution shape, no shortcuts. Just your numbers played out across thousands of possible futures.

How to Find Yours in Edge Engine

Enter your win rate, average win, average loss, risk per trade, starting balance, and number of trades in the Simulation section. Run the simulation. Your ruin risk appears in the top stats row as Ruin Risk, the percentage of simulations where the account lost 80% or more of its starting balance.

A few things to try once you have your baseline number:

Increase the number of trades. If your ruin risk is 0% over 200 trades, try 500 or 1,000. Ruin risk tends to climb with longer trade sequences because there are more opportunities for bad runs to compound.

Adjust your risk per trade. Drop it by 20-30% and re-run. Watch how sharply the ruin risk falls. This is usually the most eye-opening experiment. Small reductions in risk per trade often produce large reductions in ruin probability.

Turn on compounding. With compounding enabled, your risk scales with your account size, which means losses get smaller as the account shrinks. This naturally reduces ruin risk compared to fixed-dollar sizing, where you’re still risking the same amount even as your account declines.

What’s an Acceptable Ruin Risk?

There’s no universal rule, but here’s a practical way to think about it:

• Below 1% — very comfortable. Your sizing gives your edge plenty of room to work.
• 1% to 5% — acceptable for most traders, but worth monitoring. If it’s closer to 5%, a modest reduction in risk per trade is cheap insurance.
• Above 5% — you’re rolling the dice more than you probably realize. One in twenty paths leads to ruin. Over a career of trading, those odds catch up.
• Above 10% — your sizing is too aggressive for your edge. The strategy might be good, but the account won’t survive long enough to prove it in a meaningful number of scenarios.

The right number for you depends on your personal risk tolerance and whether you have the ability to re-fund the account if it blows. But most traders, when they actually see their ruin probability, realize they’d prefer it to be a lot lower than it is.

The Relationship Between Ruin Risk and Drawdown

Ruin risk and max drawdown are related but different. Max drawdown tells you how far the account fell from its peak. Ruin risk tells you whether the account fell far enough that it’s effectively dead.

You can have a large max drawdown, say 40%, and still recover if the edge is strong. But a 40% drawdown with aggressive sizing might leave you risking so little in dollar terms (if using compounding) or burning through capital so fast (if using fixed sizing) that recovery becomes impractical.

The drawdown distribution in Edge Engine shows you the range of drawdowns you can expect. The ruin risk figure tells you how often the worst of those drawdowns crosses the point of no return.

Next Steps

• Launch the simulator and check your ruin risk at your current sizing.
• What Are R-Multiples? — if you’re not sure how to calculate the stats you need for the simulator.
• What Risk Per Trade Should I Use? — use the optimizer to find sizing that balances performance with survival.