A streak question needs a starting point and a window. “The next ten red wagers all lose” names one ten-spin sequence. “At least ten consecutive losses somewhere in 100 spins” searches many overlapping positions. Those probabilities are different.
One specified losing sequence
For an ordinary European red wager, loss probability is 19/37 because black and zero both lose. With independent spins, k consecutive losses from a specified starting position have probability (19/37)^k.
Scroll to compare all columns
| Consecutive losses | Exact expression | Approximate probability |
|---|---|---|
| 3 | (19/37)^3 | 13.54% |
| 6 | (19/37)^6 | 1.83% |
| 10 | (19/37)^10 | 0.128% |
These figures concern losing red wagers, not exclusively black results. Ten black pockets in a specified sequence instead use (18/37)^10. Zero separates those events.
A longer session gives many possible starts
A 100-spin sequence contains 91 starting positions for a ten-spin window. Multiplying the one-window probability by 91 gives an expected number of all-loss windows, not an exact probability of at least one run. A single eleven-loss streak produces two overlapping ten-loss windows.
An exact finite-session calculation can track the current trailing-loss length while excluding paths that have already reached the target. Start with probability one at trailing length zero. After each spin, a win moves every surviving state back to zero; a loss moves state j to j+1. Any move reaching the target leaves the surviving set. After the last spin, one minus the surviving probability is the chance of at least one target run.
The streak calculator should be read according to its labeled window. Do not turn a specified-run result into an anywhere-in-session claim.
The past does not alter the next spin
After nine observed losses, the probability of another loss remains 19/37 under the fair independent model. The rarity of a ten-loss sequence before it began does not make the tenth wager safer once the first nine are known.
This distinction matters for Martingale: rising stakes arrive precisely along a losing path. Read bankroll and table limits to compare that next stake with a finite wallet, rather than assuming a win must arrive in time.
Sources and scope
- Roulette probability derivation. Amenti Labs LLC. Fair independent pockets, fixed payouts, full outside loss on zero. Formula and all supported bets regression tested.
Publication date: 2026-11-07. Checked 2026-11-07.