Streak Probability Calculator
What's the probability of hitting 5 picks in a row at a 55% win rate? Or going on a 10-loss losing streak in a season of 100 bets? This calculator answers both, plus expected longest streak in a series of bets.
Result
Formulas
- P(N wins in a row at rate p) =
p^N - P(N losses in a row at rate p) =
(1 − p)^N - P(at least one N-streak in M bets) is approximated by
1 − (1 − p^N)^(M − N + 1)for independent bets - Expected longest streak in M bets at rate p is approximately
log(M(1 − p)) / log(1 / p)
Why this matters for bankroll
Even profitable bettors with 55% win rates will hit losing streaks of 5+ bets multiple times per year. A 1000-bet season at 55% win rate has a roughly 99%+ chance of producing at least one 5-loss streak and a meaningful chance of an 8-loss streak. Bankroll sizing needs to absorb these stretches without forcing you to stop betting.
How to use this
Use this together with the Kelly Criterion calculator. Quarter Kelly stakes can survive 10-loss streaks at typical NFL win rates without major drawdown, while Full Kelly often cannot.
Frequently Asked Questions
How do I calculate the probability of a winning streak?
For independent bets at win rate p, the probability of N wins in a row is p to the power N. At 55% per bet, the probability of 5 wins in a row is 0.55^5 = 5.03%. At 50%, it's 0.5^5 = 3.13%.
What's the longest losing streak I should expect at 55% win rate?
Over 1000 bets at 55% win rate, the expected longest losing streak is around 10 bets. The calculator's expected-longest-streak field shows the rough estimate. Plan bankroll to absorb roughly 2x the expected longest streak to avoid forced stops.
Does this calculator work for parlays?
Yes. Use the parlay's combined win probability as the per-bet rate. For example, a 3-leg -110 parlay has roughly 14% win probability; the chance of cashing 3 such parlays in a row is 0.14^3 = 0.27%.
Why do streaks matter for bankroll management?
Even profitable bettors hit losing streaks. A 1000-bet season at 55% win rate has ~99% chance of producing at least one 5-loss streak and meaningful chance of an 8-loss streak. Bankroll sizing must absorb these stretches without forcing you to stop betting.
How does streak math interact with Kelly Criterion?
Quarter Kelly stakes can typically survive 10-loss streaks at typical sports betting win rates without major drawdown. Full Kelly often cannot. The streak calculator helps you stress-test the drawdown risk of your chosen stake sizing.