There's a number that every trader should know but almost none calculate: the probability that their account will be destroyed.
Not reduced. Destroyed. Wiped out completely, game over, no recovery possible.
This is called Risk of Ruin (RoR)-the statistical probability that a series of losses will reduce your account below a point where you can no longer trade effectively. It doesn't matter how brilliant your strategy is or how positive your expectancy looks on paper. If your risk of ruin is high, you're playing Russian roulette with your trading capital.
The most insidious thing about risk of ruin? It often strikes accounts that "should" have been profitable. Traders with genuine edge blow up all the time-not because they were wrong about their strategy, but because they sized too aggressively for their variance and caught an unlucky streak before the edge could manifest.
This guide will show you how to calculate your risk of ruin, understand the factors that influence it, and structure your trading so that survival is virtually guaranteed.
Risk of Ruin is the probability that you'll lose enough of your trading capital to be effectively forced out of the game. "Ruin" doesn't necessarily mean losing everything-it means reaching a point where you can no longer trade your system properly.
For most traders, ruin occurs at:
- 50% drawdown: Psychologically crushing; most people quit here
- 70-80% drawdown: Position sizes become too small to be meaningful
- 90%+ drawdown: Effectively game over
Even a system with positive expectancy will experience drawdowns. The question is whether those drawdowns will hit your ruin threshold before you recover.
The math is unforgiving:
| Drawdown |
Gain Needed to Recover |
| 10% |
11.1% |
| 20% |
25.0% |
| 30% |
42.9% |
| 40% |
66.7% |
| 50% |
100.0% |
| 60% |
150.0% |
| 70% |
233.3% |
| 80% |
400.0% |
| 90% |
900.0% |
A 50% drawdown requires a 100% return just to break even. A 75% drawdown requires 300%. This asymmetry is why avoiding large drawdowns matters more than chasing large gains.
Risk of ruin acknowledges that drawdowns can happen in strings, purely due to randomness, even when your edge is intact. A 10-loss streak with 1% risk per trade loses 10%. The same streak with 5% risk loses 40%. Same bad luck, dramatically different consequences.
Several formulas estimate risk of ruin. The most useful for traders considers win rate and risk/reward.
- For a system with fixed percentage risk per trade: RoR = ((1 - Edge) / (1 + Edge))^Units
Where:
-
Edge = (Win Rate × Win/Loss Ratio) - (1 - Win Rate)
-
Units = Number of risk units until "ruin" (e.g., if you risk 2% per trade and ruin = 50% loss, Units = 25)
-
Simplified approximation: RoR ≈ ((1 - A) / (1 + A))^(B/f)
Where:
- A = Your edge in decimal form
- B = Your ruin threshold as a fraction of capital
- f = Your fraction risked per trade
Let's calculate RoR for a system with:
- Win rate: 55%
- Average win: 1.5R (150% of risk)
- Average loss: 1R
- Risk per trade: 2%
- Ruin threshold: 50%
Step 1: Calculate edge
Edge = (0.55 × 1.5) - (0.45 × 1.0) = 0.825 - 0.45 = 0.375
Step 2: Calculate units to ruin
Units = 0.50 / 0.02 = 25
Step 3: Apply formula
RoR = ((1 - 0.375) / (1 + 0.375))^25
RoR = (0.625 / 1.375)^25
RoR = (0.4545)^25
RoR = 0.0000000001 (essentially zero)
With these parameters, ruin is virtually impossible. The edge is strong enough and position size small enough that even worst-case scenarios don't reach ruin.
Now let's increase risk to 5% per trade:
Units = 0.50 / 0.05 = 10
RoR = (0.4545)^10
RoR = 0.00034 = 0.034%
Still very low. But watch what happens when we double risk again to 10% per trade:
Units = 0.50 / 0.10 = 5
RoR = (0.4545)^5
RoR = 0.018 = 1.8%
Now there's nearly a 2% chance of ruin. Trade long enough, and you'll hit ruin eventually.
This is the critical insight most traders miss: positive expectancy does not guarantee survival.
You can have a system with 55% win rate, great risk/reward, and positive expectancy-and still blow up. Here's why.
Expectancy tells you the average outcome over infinite trades. But you don't trade infinite trades. You trade a finite sequence, and within that sequence, variance can produce devastating losing streaks even with positive expectancy.
A 55% win rate system has a 45% per-trade loss probability. The probability of losing 5 trades in a row is 0.45^5 = 1.8%. That happens roughly every 55 trades on average.
The probability of losing 10 in a row? 0.45^10 = 0.034%. Sounds rare, but trade for 3,000 trades (a few years of active trading) and you'll probably see it.
At 10% risk per trade, 10 consecutive losses means a 65% drawdown. For most traders, that's ruin.
-
Consider two traders with identical systems: Trader A: Starts with winners, suffers losses later when account is larger. Drawdown is 20% from a higher base.
-
Trader B: Starts with a brutal losing streak, then wins. Account drops 40% before recovering.
Same trades, different sequence. Trader B might have quit at the 40% drawdown, never experiencing the recovery.
This is pure luck. Neither trader did anything different. But Trader B's capital and psychology were tested far more severely.
In crypto, leverage makes everything worse. A system that's safe at 1x leverage can be suicidal at 5x.
| Risk/Trade (1x) |
Equivalent Risk (5x) |
10-Loss Streak Impact |
| 2% |
10% |
-65% |
| 3% |
15% |
-80% |
| 5% |
25% |
-94% |
That 5% "conservative" risk becomes 25% effective risk with 5x leverage. Ten bad trades-which will happen eventually-and you're destroyed.
Understanding what drives RoR helps you minimize it.
Position size is the dominant factor in risk of ruin. Double your position size and your RoR can increase by orders of magnitude.
The relationship is exponential, not linear. Going from 1% to 2% risk doesn't double your RoR-it might increase it 10x or more depending on your edge.
Lower win rates mean more losing streaks, which increases RoR.
| Win Rate |
Probability of 5-Loss Streak |
| 60% |
1.0% |
| 55% |
1.8% |
| 50% |
3.1% |
| 45% |
5.0% |
| 40% |
7.8% |
A 40% win rate system (which can be profitable with good risk/reward) has nearly 8x higher chance of a 5-loss streak than a 60% win rate system.
Better risk/reward reduces RoR in two ways:
- Higher expectancy means faster recovery from drawdowns
- Larger winners offset the psychological impact of losing streaks
A system with 2:1 R/R can survive more losses than a 1:1 system, even with the same win rate.
Smaller accounts have higher RoR because:
- Minimum position sizes force larger percentage risk
- Less margin for error
- Faster ruin in absolute terms
If the minimum position size on your exchange forces you to risk 5% per trade, your RoR is dramatically higher than someone who can risk 0.5%.
Mathematical ruin might be 100% loss. Practical ruin is wherever you'd stop trading-often 30-50% loss. This is your real ruin threshold.
Setting a lower ruin threshold for the formula actually helps-it forces more conservative sizing to protect against the drawdown where you'd actually quit.
If your losses tend to cluster (trending market goes against all your positions), RoR increases compared to independent losses. Diversification across uncorrelated strategies reduces this clustering effect.
Let's make this concrete with your own numbers.
You need:
- Win rate (from your trade journal)
- Average R-multiple on winners
- Average R-multiple on losers
- Current risk per trade
Example data:
- Win rate: 48%
- Average win: 2.2R
- Average loss: 1.0R
- Risk per trade: 2%
Edge = (Win Rate × Avg Win) - (Loss Rate × Avg Loss)
Edge = (0.48 × 2.2) - (0.52 × 1.0)
Edge = 1.056 - 0.52
Edge = 0.536R per trade
This is positive expectancy of 0.536R per trade-a decent edge.
What drawdown would make you stop trading?
For most traders:
- Comfortable threshold: 30%
- Painful threshold: 50%
- Absolute threshold: 70%
Let's use 50% as our ruin point.
Units = Ruin Threshold / Risk per Trade
Units = 0.50 / 0.02 = 25 units
RoR = ((1 - Edge) / (1 + Edge))^Units
But wait-this formula uses edge as a ratio, not R-multiples. We need to convert.
For R-multiple edge:
RoR ≈ e^(-2 × Edge × Units)
RoR ≈ e^(-2 × 0.536 × 25)
RoR ≈ e^(-26.8)
RoR ≈ essentially 0%
With this edge and 2% risk, ruin is virtually impossible. You'd need catastrophically unlucky variance.
Now see how RoR changes with different assumptions:
| Risk/Trade |
Units to Ruin |
Approx RoR |
| 2% |
25 |
~0% |
| 3% |
17 |
~0.01% |
| 5% |
10 |
0.2% |
| 7% |
7 |
2% |
| 10% |
5 |
15% |
Even with solid edge, 10% risk per trade creates 15% probability of ruin. One in seven traders with this system would blow up.
Knowing about risk of ruin doesn't mean traders act on it. Several psychological biases prevent rational RoR management.
Traders believe bad things happen to other people. "I'm skilled enough to avoid losing streaks." But losing streaks aren't about skill-they're about probability. Everyone gets them.
The better a trader's recent performance, the higher their overconfidence. Ironically, winning streaks often precede blow-ups because winners size up aggressively.
If you haven't experienced a major drawdown recently, you underestimate its probability. Humans weight recent experience too heavily when assessing risk.
A trader on a hot streak might think "I haven't lost 5 in a row in months-it won't happen now." The probability is unchanged; only their perception shifted.
Proper risk management means smaller position sizes, which means slower equity growth. Many traders can't tolerate slow growth, so they size up to accelerate returns-increasing RoR in the process.
The irony: the rushed traders often end up with no returns at all because they blew up. The patient traders finish wealthy.
"I've lost 4 in a row, so I'm due for a win. I'll size up to recover faster."
This is catastrophically wrong. Previous losses don't affect future probabilities (assuming independent trades). Sizing up after losses increases RoR precisely when the account is most vulnerable.
Traders anchor psychologically to their starting balance. After doubling their account, they feel they're playing with "house money" and can take more risk.
But the doubled account is your money now. A 50% drawdown from the doubled account puts you back at start. A 50% drawdown from an account that's still at original value puts you at 50% of start.
House money is a dangerous illusion.
If position sizing is the dominant factor in RoR, how should you size positions?
Risk a constant percentage of current account value per trade.
Advantages:
- Automatically scales down after losses (reducing ruin risk)
- Automatically scales up after wins (compounding growth)
- Simple to implement
Implementation:
-
Calculate 1-2% of current account balance
-
Divide by distance to stop loss (in asset terms)
-
Result is your position size
-
Example: Account: $10,000
Risk: 2% = $200
Entry: $70,000 BTC
Stop: $68,000 (2.86% below entry)
Position size: $200 / 0.0286 = $6,993 worth of BTC = 0.1 BTC
-
Kelly Criterion gives mathematically optimal sizing: Kelly % = (Win Rate × Avg Win - Loss Rate × Avg Loss) / Avg Win
-
Or in R terms: Kelly % = Edge / Avg Win (in R)
-
For our earlier example: Kelly = 0.536 / 2.2 = 24.4%
Full Kelly is too aggressive for most traders-the swings are brutal. Use fractional Kelly:
| Fraction |
Risk/Trade |
RoR Level |
Equity Volatility |
| Full Kelly |
24% |
Very high |
Extreme |
| 50% Kelly |
12% |
High |
High |
| 25% Kelly |
6% |
Moderate |
Moderate |
| 10% Kelly |
2.4% |
Low |
Low |
Most professional traders use 10-25% Kelly. The reduced return is worth the dramatically lower ruin probability.
For smaller accounts, the Fixed Ratio method provides another framework:
- Set a "delta" amount (e.g., $500 in profits needed to increase position by 1 unit)
- Start with 1 unit position
- After accumulating delta in profits, add 1 unit
- Scale back down when equity declines
This method is more conservative than fixed percentage for smaller accounts, which often need more protection.
Professional traders think differently about risk. Their primary objective isn't maximizing returns-it's ensuring survival.
A dead account can't compound. A living account, even with modest returns, eventually grows through the magic of compounding.
The expected value of aggressive sizing might look higher on a spreadsheet. But once you account for the probability of ruin (which produces zero future value), conservative sizing often has higher true expected value.
Trading is an infinite game if you don't blow up. The traders who build real wealth aren't the ones with the best year-they're the ones who stayed in the game for decades.
Jeff Bezos didn't build Amazon's wealth through one aggressive bet. He survived and compounded for 25+ years. Trading wealth works the same way.
Frame RoR as a constraint, not a variable to optimize:
Wrong: "I'll accept 5% RoR for 30% higher returns"
Right: "RoR must be below 1%. What returns can I achieve within that constraint?"
Making RoR a hard constraint prevents the slippery slope of "just a little more risk."
- You know your exact RoR (you've calculated it)
- Your position sizes feel "too small" sometimes
- You'd rather miss opportunities than take excessive risk
- You have explicit rules for reducing size during drawdowns
- Recovery from losses takes time-and you're okay with that
Even careful traders sometimes approach dangerous drawdown levels. Here's how to handle it.
- Establish explicit rules before you need them: At 20% drawdown:
- Review all recent trades for execution errors
- Confirm system parameters haven't drifted
- Reduce position sizes by 25%
At 35% drawdown:
- Reduce position sizes by 50%
- Stop trading for 1 week minimum
- Comprehensive review of strategy performance
At 50% drawdown:
- Stop trading immediately
- Full audit: Is the edge still there?
- Consider whether to continue or reset
Having rules written in advance prevents emotional decision-making during stress.
The worst response to drawdown is aggressive position sizing to recover faster. This dramatically increases RoR exactly when your account is most vulnerable.
Math check: A 40% drawdown requires 67% gain to recover. Increasing risk might speed recovery-or accelerate ruin. The asymmetry favors caution.
Sometimes the right answer is to stop, reassess, and restart with fresh capital if you determine your edge is real.
Continuing to trade a damaged account with compromised psychology often leads to worse decisions. A clean start-with lessons learned-can be more valuable than grinding back from a hole.
Whatever caused the drawdown is valuable information. Document it thoroughly:
- Market conditions during the period
- Your trades and their outcomes
- Any rule violations or execution errors
- Psychological state throughout
This documentation becomes training material for avoiding future drawdowns.
Professional traders typically target RoR below 1%, often below 0.1%. At these levels, ruin is extremely unlikely. Retail traders should aim for under 5% to have reasonable survival probability over a multi-year trading career.
Reduce position size. It's the single most effective lever. Cutting position size in half can reduce RoR by 90% or more. Improving win rate or risk/reward also helps but takes much longer.
Technically, you can only lose 100% in spot (no liquidation). But practical ruin-the point where you stop trading-occurs much earlier. Use a 50-70% drawdown as your ruin threshold for spot trading.
Leverage multiplies effective position size and thus dramatically increases RoR. 5x leverage on a 2% risk trade is equivalent to 10% risk-which has vastly higher ruin probability. Add liquidation risk and leverage is even more dangerous.
Expectancy is an average over many trades. In any finite sequence, variance can produce results far worse than average. Risk of ruin is the probability that this variance produces enough losses to end your trading before the positive expectancy manifests.
Recalculate whenever your trading parameters change significantly: new strategy, different win rate, changed position sizing. Also recalculate periodically (quarterly) to ensure your estimates remain accurate as you accumulate more data.
Most traders obsess over returns, win rates, or impressive trades. These metrics are secondary.
The ultimate metric is survival.
A 100% return means nothing if you blow up the following year. A 50% win rate means nothing if your position sizing creates a 20% chance of ruin. A spectacular trade means nothing if it encourages risk-taking that eventually destroys your account.
Risk of ruin is the number that tells you whether you'll still be trading in 5 years. Whether your edge has time to compound. Whether all your other metrics matter at all.
Calculate your RoR. Make it your primary constraint. Size positions so that survival is virtually guaranteed.
Then let time and compounding do their work.
Calculating risk of ruin requires accurate trade statistics, complex formulas, and ongoing monitoring. Most traders never do it-and many pay the ultimate price.
Thrive makes survival math automatic.
✅ Automatic RoR Calculation - Import your trades and Thrive calculates your risk of ruin based on your actual statistics, not theoretical assumptions.
✅ Position Size Recommendations - Get suggestions for position sizing that keeps RoR below your specified threshold.
✅ Drawdown Monitoring - Track your current drawdown against historical norms and ruin thresholds. Know when you're approaching danger.
✅ Monte Carlo Integration - See RoR in context with Monte Carlo simulations showing full distribution of possible outcomes.
✅ Weekly AI Coach - Get personalized feedback on your risk management, including warnings when your sizing approaches dangerous territory.
✅ Drawdown Alerts - Automatic notifications when you hit predetermined drawdown levels, so you can implement your protocol before emotions take over.
The traders who survive long enough to build real wealth aren't the aggressive ones. They're the ones who understood ruin probability and refused to let it happen.
Calculate your survival. Guarantee it.
→ Start Managing Your Risk of Ruin
