Losing Streak Calculator

How to use it

1. 1 Enter your win rate per bet as a percentage.
2. 2 Enter the number of bets, from 1 to 5,000.
3. 3 Enter the streak length, from 1 to 50 losses in a row.
4. 4 Read the chance of at least one such streak and the longest streak you should expect.

Streaks are more common than they feel

Bettors tend to think of a streak as a rare event, but it only has to appear once anywhere in the run. A 50% bettor has about an 81% chance of at least one 5-loss streak in 100 bets, and a better than even chance of a 6-loss streak.

Knowing that helps you tell a normal run of variance from a real problem, and it is a good reason to size bets small enough to survive one.

How the exact probability is calculated

The calculator tracks the current run of consecutive losses bet by bet. After each bet the run either grows by one (a loss) or resets to zero (a win), and any probability that reaches your streak length is counted as a streak. This is exact for independent bets and does not use the common shortcut of multiplying the odds of one streak by the number of places it could start, which overcounts.

It assumes every bet has the same win rate and that bets do not affect each other. Real results will differ if your win rate changes by bet type or over time.

Worked example

A 50% win rate over 100 bets, looking for 5 losses in a row. The chance of at least one such streak is 81.01%. The chance that the next 5 bets all lose is 3.13% (1 in 32). The longest streak with at least a 50% chance of appearing in 100 bets is 6 losses (54.6%); a 7-loss streak is below 50%.

The formula

Frequently asked questions