Streak Probability Calculator

Calculate the probability of hitting a winning or losing streak over any number of bets. Understand why cold streaks are mathematically inevitable, and plan your bankroll accordingly.

Presets:

Inputs

Streak Type

Win Probability 55.0%

Number of Bets / Trials total sample

bets

Streak Length to Check consecutive outcomes

in a row

Results

Probability of a 5-loss streak

64.7%

Likely

64.7%

0%25%50%75%100%

Expected Streaks0.98in 100 bets

Avg. Bets to First Streak97bets on average

Longest Expected Streak5.3consecutive losses

Single-Trial Prob1.8%q^k = 0.4500⁵

Even with a 55% win rate, there's a 65% chance you'll hit a 5-bet losing streak in 100 bets. More likely than not, so plan your bankroll for it.

Streak Probability Table

Probability of hitting each streak length in 100 bets (losing streaks, 55% win rate)

Streak	Probability	Expected #
1	~100%	25.0
2	~100%	11.1
3	99.8%	4.95
4	91.5%	2.21
5	64.7%	0.98
6	36.3%	0.44
7	17.9%	0.19
8	8.4%	0.09
9	3.8%	0.04
10	1.7%	0.02
11	0.76%	< 0.01
12	0.34%	< 0.01
13	0.15%	< 0.01
14	0.07%	< 0.01
15	0.03%	< 0.01

Risk of Ruin by Bankroll Depth

Probability of going broke within 100 flat bets at 55% win rate

Bankroll	Bust Probability	That Many Losses In A Row
5 units	32.0%	64.7%
10 units	9.0%	1.7%
15 units	2.1%	0.03%
20 units	0.42%	< 0.01%
25 units	0.07%	< 0.01%
30 units	< 0.01%	< 0.01%
50 units	< 0.01%	0%
75 units	< 0.01%	0%
100 units	< 0.01%	0%

Busting means your cumulative losses reach your bankroll, which takes no unbroken run at all. The third column is the chance of losing that many bets back-to-back, and it is a different and usually much rarer event: at a 50% win rate over 500 bets, a 20-unit bankroll busts 37% of the time while 20 straight losses happen 0.02% of the time. Assumes flat betting, one unit per bet at even money. Martingale or progressive systems increase bust risk dramatically.

Understanding Streaks in Gambling

Why Losing Streaks Are Normal

Even with a 55% win rate, the probability of hitting a 5-bet losing streak in 200 bets is 88.0%. Streaks are not a sign of bad luck, they are a guaranteed feature of random variance. The longer you play, the longer your worst streak will be. A 50% bettor playing 1,000 bets hits a 10-loss streak 38.5% of the time, and needs about 2,000 bets before that becomes more likely than not.

The Gambler’s Fallacy

After 7 losses in a row, many bettors feel they’re “due” for a win. This is false. Each bet is independent, and the coin has no memory. The probability of losing the 8th bet is exactly the same as the 1st. Streaks feel like patterns, but they are just clusters of randomness. Never increase bet size because you think a streak “must end.”

Bankroll Sizing for Streaks

Do not size your bankroll off your longest expected streak. It is the intuitive move and it is roughly half the answer. A break-even bettor over 1,000 flat bets has a worst expected losing streak of about 9, but 30 units still goes broke 34% of the time, because losses accumulate through ordinary choppy stretches rather than in one unbroken run. Holding to a 5% risk of ruin over those 1,000 bets takes about 62 units. Streak length grows like a logarithm of the number of bets, so it barely moves. The bankroll you need grows like a square root, so it keeps climbing. Read the risk-of-ruin table above, not the streak table.

Streak Length vs Sample Size

The longest expected streak grows logarithmically with sample size. For a break-even bettor: about 6 in 100 bets, about 9 in 1,000, about 13 in 10,000. Ten times the bets buys you roughly three more consecutive losses. So the more you play the worse your worst streak gets, but it grows slowly, and slowly enough that sizing a bankroll off it will leave you short. Use this calculator to plan for the right sample size and avoid being shocked when variance hits.

Protect Your Bankroll from Streaks

GAMB·8's automated bot strategies include built-in stop-loss limits, streak detection alerts, and Kelly-optimal position sizing, so a bad streak doesn't wipe out your balance.