Losing streak calculator
How likely is a run of losses, given your win rate and number of trades? Higher than most people expect.
Calculations run in your browser. Nothing you type is sent or stored. Results are estimates for information only, not investment advice.
How it works
Write p for the win rate, q = 1 − p for the loss rate and n for the number of trades. The chance u(n) that n trades contain no run of L or more losses follows a simple recurrence: u(i) = 1 for i < L, u(L) = 1 − qL, and u(i) = u(i−1) − p × qL × u(i−L−1) for i > L. The chance of at least one such run is 1 − u(n). The longest-streak rows search for the shortest streak length m for which the chance of a longer streak is at most 50% (median) or 5%. Trades are treated as independent, each winning with probability p.
Worked example
The page opens with a 40% win rate, 200 trades and a test of 8 losses in a row. The chance of at least one run of 8 or more losses is 75.0%. Half of all 200-trade runs have a longest streak of 9 or fewer, and 19 out of 20 have 14 or fewer. Our 4-hour trend rule won 36.4% of 1,037 trades (the first button): the calculator gives a median longest streak of 13, 19 at the 95% level and a 23.5% chance of a streak of 16 or more. The longest streak in the replay was 16.
Longest losing streak by win rate
| Win rate | 100 trades | 500 trades | 1,000 trades |
|---|---|---|---|
| 30% | 10 / 17 | 15 / 22 | 17 / 24 |
| 40% | 7 / 12 | 11 / 16 | 12 / 17 |
| 50% | 6 / 9 | 8 / 12 | 9 / 13 |
| 60% | 4 / 7 | 6 / 9 | 7 / 10 |
Questions
How many losses in a row should I expect?
It depends on the win rate and on how many trades you make. At 50% over 100 trades, half of all runs have a longest streak of 6 or fewer and 19 in 20 have 9 or fewer. At 30% over 1,000 trades the same figures are 17 and 24. The lower the win rate, the longer the streaks, and more trades give them more chances to appear.
Does a long losing streak mean the strategy stopped working?
Not by itself. Long streaks are the normal price of a low win rate: a rule that wins 36% of its trades loses 16 in a row in about one 1,037-trade run in four. If trades are independent, a streak does not change the odds of the next trade. In our replay of the 4-hour trend rule, the 90 days after four straight losses were positive 76% of the time, against 71% at any time. More on that. Judging a strategy takes many trades: how many trades to prove a strategy.
My trades are not independent. Can I still use this?
As a guide, yes. Trades taken in the same market conditions can lose together, so real streaks can be longer than this calculator shows. Treat the result as a floor, not a ceiling.