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Losing Streak Calculator

Get the probability of hitting a losing streak over a planned sample of forex or CFD trades, from your win rate and trade count. It uses an exact dynamic-programming model and runs in your browser.

Direct answer

For loss probability q, the isolated chance of exactly k losses in a row is q^k. The probability of at least one k-loss run inside N trades is computed with an exact no-run dynamic program, then subtracted from 1.

Sequence inputs

The DP result estimates at least one run of this length or longer inside the trade count.
P(at least one k-loss run) = 1 − P(no k-loss run)

Loss-run estimate

At least one streak—
Pure k-loss sequence—
Expected longest losing streak—
Loss probability q—
The probability is a model estimate under independent trade outcomes.
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How it works

What this calculator answers

The tool estimates whether a run of at least k consecutive losses appears somewhere inside N trades. That is different from q^k, which only describes one specific k-loss sequence.

Dynamic-programming model

The engine tracks the current tail length of consecutive losses from 0 to k-1. A win resets the state to 0. A loss moves the state up by 1. Paths that would reach k are excluded from the no-run total.

P(at least one k-loss run) = 1 - P(no k-loss run)

E[longest loss streak] = sum over k of P(at least one k-loss run)

Worked example

With a 45% win rate, the loss probability is 55%. Over 20 trades, the model estimate for at least one 3-loss run is about 86.9127%. The isolated probability of three losses in one specific block is 0.55^3 = 16.6375%.

Important limits

This model assumes independent outcomes and a stable win rate. Real trade outcomes can cluster by regime, news conditions, setup quality or execution quality, so the result should be treated as a model estimate.

Frequently asked questions

Why is the N-trade probability higher than q^k?
Because there are many possible places for the streak to appear inside N trades. The DP counts all valid placements without double-counting through simulation.
Does the calculator use random simulation?
No. It is an analytic dynamic-programming calculation, so the same inputs always produce the same output.
What does expected longest losing streak mean?
It is the sum of probabilities that at least one streak reaches each possible length from 1 to N.
Can I use this with a discretionary strategy?
Yes, but only as a model estimate. If your win rate shifts by setup type or market regime, test several input cases.
Should I size trades from this result alone?
No. Combine it with position sizing, account drawdown tolerance and your actual cost structure.

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