Risk of ruin calculator
Calculate the probability of losing your entire bankroll based on your win rate, average odds, and stake size.
Percentage of bets you win over a large sample.
What percentage of your bankroll you stake per bet.
Risk of ruin: 1.76%
| Risk of ruin | 1.76% |
| Expected value per bet | +£5.00 |
| Edge | +10.0% |
| Average profit per winning bet | £50.00 |
| Average loss per losing bet | £50.00 |
| Bets to double bankroll (expected) | ~200 |
| Bets to go bust (worst case losing streak) | 20 |
Risk of ruin by stake size
| Stake Size | Risk of Ruin | Bets Before Bust |
|---|---|---|
| 1% | <0.01% | 100 |
| 2% | <0.01% | 50 |
| 3% | 0.12% | 33 |
| 5% | 1.76% | 20 |
| 10% | 13.26% | 10 |
| 20% | 36.42% | 5 |
What is risk of ruin?
Risk of ruin is the probability of losing your entire bankroll before doubling it (or reaching some other target). Even profitable bettors face risk of ruin if they stake too aggressively. A 55% win rate at evens is profitable long-term — but staking 20% per bet gives a real chance of going bust before the edge plays out.
Why stake size matters more than win rate
A bettor with a 55% win rate staking 2% per bet has a negligible risk of ruin. The same bettor staking 20% per bet has a meaningful chance of going bust. The edge is the same — the difference is entirely in how much you risk per bet. This is why bankroll management exists.
If you don't have an edge
If your expected value per bet is negative (which it is for all casino games and for most recreational sports bettors), your risk of ruin is 100% given enough time. The only variable is how quickly. Smaller stakes slow the process; larger stakes accelerate it. The calculator will show this honestly.
How risk of ruin works
The maths
Risk of ruin depends on three factors: your edge (expected value per bet), your stake size relative to your bankroll, and variance in outcomes. The formula uses an exponential approximation: RoR ≈ e^(−2 × EV × bankroll_units / variance). A larger edge or smaller stakes dramatically reduce ruin probability.
Edge is everything
Your edge = (win_rate × decimal_odds) − 1. If this is zero or negative, your risk of ruin is 100% over time — no amount of bankroll management changes this. Bankroll management only matters when you have a genuine edge to protect.
The stake size effect
Halving your stake size doesn't just halve your risk — it reduces it exponentially. Going from 10% to 5% stakes might take your risk of ruin from 30% to 5%. Going from 5% to 2% might take it from 5% to near zero. This is why most professionals stake 1–3% of their bankroll per bet.