Drawdown & risk-of-ruin calculator
Probability of losing X% of bankroll over N bets
Calculate the probability of significant bankroll drawdowns over a series of bets — even with positive edge.
Why drawdowns matter even with edge
A bettor with 5% edge using full Kelly still has a 13% chance of losing 50% of bankroll before doubling. Most don't psychologically survive a 50% drawdown — they tilt and overbet. This calculator estimates your drawdown probabilities so you can choose a Kelly fraction you'll actually stick to during losing streaks. Combine with Stop-loss planner for session-level protection.
See also: Kelly criterion, Kelly fraction comparison, Stop-loss planner
How to use
- 1Enter your edge per bet (%).
- 2Enter your bet size as % of bankroll.
- 3Enter number of bets considered.
- 4See probabilities of -25%, -50%, -75% drawdowns.
Example: 3% edge, full Kelly
3% edge, 6% bet size (full Kelly equivalent), 500 bets. Risk of 25% drawdown: ~45%. Risk of 50% drawdown: ~12%. Risk of going bust: ~2%. Half Kelly (3% bet) cuts all these in half. Quarter Kelly: barely any drawdown risk but slower growth.
When to use
- Choosing your Kelly fraction realistically
- Setting expectations before a long betting campaign
- Understanding why pros use Half or Quarter Kelly
Frequently asked questions
What is the Drawdown calculator calculator?
A bettor with 5% edge using full Kelly still has a 13% chance of losing 50% of bankroll before doubling. Most don't psychologically survive a 50% drawdown — they tilt and overbet.
How does the Drawdown calculator calculator work in practice?
3% edge, 6% bet size (full Kelly equivalent), 500 bets. Risk of 25% drawdown: ~45%. Risk of 50% drawdown: ~12%. Risk of going bust: ~2%. Half Kelly (3% bet) cuts all these in half. Quarter Kelly: barely any drawdown risk but slower growth.
When should I use the Drawdown calculator calculator?
Choosing your Kelly fraction realistically. Setting expectations before a long betting campaign. Understanding why pros use Half or Quarter Kelly.