Martingale simulator
Doubling after a loss feels safe because one paying bet recovers every loss before it. The catch is the losing streak that empties the bankroll first. Run it 1,000 times and count.
Simulator
Pick a starting point or enter your own numbers. The bet doubles after every loss and returns to the base bet after every paying bet.
1,000 simulated sessions
Sessions that went bust
64.3%
- 357 of 1,000
- 98.16 (from 100)
- 64
- 6 in a row
- 1.66%
- −1.0%
How the simulation works
Each session starts with the bankroll and the base bet. After a losing bet the next bet doubles; after a paying bet it returns to the base bet. A session goes bust when the next bet is more than what is left, and otherwise stops after the set number of rounds.
Each bet has two outcomes, with the chance and payout you set. Bets with several payout levels are not modelled here.
Doubling changes how losses arrive, not their average size. Every bet keeps the same average return, so the session keeps it too: many small gains, paid for by rare large losses.
A bankroll B with base bet b pays for k losses in a row, the largest k with b × (2^k − 1) ≤ B. After those k losses the next bet cannot be placed. The chance that k given bets all lose is (1 − p)^k, where p is the chance a bet pays.
The belief
Doubling after a loss is one of the four myths the lab checks.