Losing Streak Calculator
Find the chance of consecutive losses across a whole series of trades.
How it works
The calculation tracks every possible unfinished loss run and adds the probability of reaching the tested length. It solves the independent-trade model numerically, with no random simulation. A streak may start at many positions in the sample; the probability for one fixed block is a different quantity.
Win rate stays constant, outcomes are independent wins or losses, and the starting losing run is zero. Real trade outcomes may be correlated. Break-even outcomes are not a separate state in this model.
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How the Losing Streak Calculator works
This losing streak probability calculator finds the chance of at least one run of k or more consecutive losses within N trades. Enter a constant win rate, the number of trades and the losing-streak length. It solves the independent-trade model numerically rather than simulating random trade paths.
A losing streak anywhere in the sample
A run can start at many different positions. The formula (1 − win rate)^k gives the probability that one specific block of k trades all loses. It does not give the chance that such a block occurs somewhere in a longer sample. Neighboring blocks overlap, so treating all possible starting positions as independent also gives the wrong answer.
The calculation keeps probabilities for unfinished runs of 0 through k − 1 losses. A win resets the run to 0, while a loss extends it. Once the run reaches k, that probability is counted in the event and cannot be counted again. This accounts for overlapping runs over the full trade horizon.
Worked example: 45% win rate over 200 trades
Enter a 45% win rate, 200 trades and a streak length of 8. The chance of the next eight trades all losing is 0.55⁸, approximately 0.84%. The chance of at least one run of eight or more losses somewhere in the 200 trades is approximately 53.04%.
Those values answer different questions. A long trade sample offers many opportunities for a losing run to start, even though one particular block is unlikely. Changing the number of trades changes the full-sample probability; it does not change the probability for the next fixed block.
Inputs, limits and model assumptions
Win rate ranges from 0% to 100%. Trade count is a whole number from 0 to 2,000, and streak length is a whole number from 1 to 2,000. The calculation starts with no losing run already in progress. If the streak is longer than the trade sample, the full-sample probability is zero, while the separately shown next-block probability still describes that future block.
Each trade has the same win probability and the outcomes are independent wins or losses. Real outcomes may cluster, the win rate may change and break-even trades may occur; those effects are not modeled. The result is a probability under the entered assumptions, not a prediction of a specific sequence.
The calculation does not size your trades or convert a run into a cash drawdown. Use position sizing for cash risk per trade, drawdown recovery for recovery arithmetic and risk of ruin for the probability of reaching an account-loss threshold under that tool's assumptions.
FAQ
Does a streak length of 8 include 9 or 10 losses in a row?
Yes. The event is at least one run of eight or more losses, not exactly eight. Once a sequence reaches eight losses it has already met the condition.
Why not multiply the number of possible streaks by the block probability?
A long losing run creates overlapping blocks, so the same sequence can be counted several times. Multiplication does not give the probability of at least one run. The state-based calculation counts each sequence in that event once.
Is this the same as the probability of ruin?
No. Streak probability depends on win rate, trade count and run length. Ruin also depends on position sizing, payoffs and the account-loss threshold. A series can reach a drawdown threshold without containing the particular streak tested here.