You can have a positive-edge strategy and still go broke before the edge has time to show. That is the practical meaning of risk of ruin: the probability that variance, bet sizing and bankroll size combine badly enough to wipe out your bankroll or push it below a defined survival threshold.
This Risk of Ruin Calculator estimates bankroll survival from four core inputs: bankroll, fixed bet size, win rate and average decimal odds. It also shows break-even win rate, expected value per bet, bankroll units, wipeout-streak risk and an estimated safer stake size for a lower ruin target.
Important: this is a simplified fixed-stake model. It assumes independent bets, stable average odds and a consistent win rate. Real betting results can differ because of changing bet sizes, correlated bets, market limits, bookmaker restrictions, commission, changing odds and inaccurate edge estimates.
Risk of Ruin Calculator
Estimate bankroll survival from fixed stake, win rate and average odds.
How to Use the Risk of Ruin Calculator
- Enter bankroll: the total amount reserved for betting or play.
- Enter unit size: the fixed stake per bet. Do not use your maximum possible bet unless that is your normal stake.
- Enter win rate: your estimated long-run win percentage.
- Enter average odds: the typical decimal price you bet, such as 1.91, 2.00 or 2.50.
- Set session bets: optional, used to estimate wipeout-streak risk over a defined number of bets.
For the full bankroll and variance toolkit, use the Bankroll Risk Calculators Hub. For stake sizing from edge, use the Kelly Criterion Calculator. For sports-betting drawdowns and confidence ranges, use the Sports Betting Variance Calculator.
What Risk of Ruin Measures
Risk of ruin estimates the chance that your bankroll fails before the long-run average has time to matter. This can happen even with a small edge if your stake is too large relative to bankroll.
| Input | Why it matters |
|---|---|
| Bankroll | Larger bankroll gives more units and more room to absorb variance. |
| Unit size | Larger bets increase drawdown speed and ruin risk. |
| Win rate | Higher win rate improves survival only if the odds support positive EV. |
| Average odds | Break-even win rate changes with price. At 2.00 odds, break-even is 50%; at 1.91, it is about 52.36%. |
Break-Even Win Rate and Positive Edge
The calculator first checks whether your inputs have positive expected value.
Break-Even Win Rate = 1 ÷ Decimal Odds
For example:
- At 2.00 odds, break-even is 50.00%.
- At 1.91 odds, break-even is about 52.36%.
- At 2.50 odds, break-even is 40.00%.
If your win rate is below the break-even point, the long-run expected value is negative. In an indefinite repeated-betting model, long-run ruin risk is effectively 100% unless you stop first.
Example: Over-Betting a Winning Strategy
Assume a bettor has a real edge:
- Average odds: 2.00
- Win rate: 55%
- Bankroll: $1,000
Scenario A: $100 Bets
A $100 stake means the bankroll has only 10 units. A normal losing streak can do serious damage before the edge has time to appear. Even with positive EV, the survival risk is materially higher.
Scenario B: $20 Bets
A $20 stake gives 50 units. The same edge is now spread across more betting opportunities, which sharply reduces the probability that variance wipes out the bankroll.
The strategy did not change. Only the stake size changed. This is why bet sizing is often the easiest way to reduce ruin risk.
Risk of Ruin vs Variance vs Losing Streaks
| Metric | What it answers | What it does not answer |
|---|---|---|
| Risk of ruin | What is the chance of bankroll failure? | Whether your edge estimate is accurate. |
| Variance | How wide can short-term results swing? | Whether you will go broke before recovery. |
| Losing streak probability | How likely is a run of losses? | Total bankroll survival when wins and losses are mixed. |
| Kelly sizing | How much to stake from estimated edge? | Whether the edge estimate is reliable. |
Model Assumptions
This calculator uses an exact even-money formula when the odds are close to 2.00 and a diffusion-style approximation for unequal decimal odds. That is useful for planning, but it is not a replacement for a full simulation when bet sizes, odds and edge vary across bets.
- Assumes a fixed stake per bet.
- Assumes independent outcomes.
- Assumes your win rate and average odds are stable.
- Assumes no betting limits, withdrawals, deposits or stake changes.
- Uses long-run approximation for non-even-money odds.
Frequently Asked Questions
What is risk of ruin?
Risk of ruin is the probability that your bankroll reaches zero or a defined ruin threshold before your edge has enough time to overcome variance.
What is a safe risk of ruin?
There is no universal safe number, but many disciplined bettors aim for less than 1% ruin risk. Anything above 5% usually means the bet size is aggressive relative to bankroll and edge.
Why does the calculator show 100% risk?
If your expected value is zero or negative, long-run ruin risk is effectively 100% in an indefinite repeated-betting model. The only way to avoid that is to stop before variance and house edge exhaust the bankroll.
How can I lower risk of ruin?
The practical ways are to reduce bet size, increase bankroll, improve the real edge, or reduce the number of bets placed. The easiest lever is usually smaller unit size.
Can a positive-edge bettor still go broke?
Yes. If the stake is too large relative to bankroll, normal losing streaks can wipe out the bankroll before the edge has time to show.
Does this calculator work for poker?
This page uses a simplified fixed-stake betting model. For poker, use a poker-specific risk of ruin model that includes winrate and standard deviation.
Responsible gambling notice: risk tools estimate mathematical exposure. They do not guarantee profit, prevent losses or make gambling safe. Never risk money you cannot afford to lose.