What it means
The idea comes from gambling. You bet a fixed amount, and if you lose you bet double, then double again, until you win; at that point the winning bet repays every previous loss plus one original stake of profit.
The logic seems airtight because a run of losses cannot go on forever. The flaw is that the stake grows exponentially, so a run of only seven or eight losses can demand a bet far larger than the original budget, and nobody can place bets without limit.
Some traders apply the same approach to markets, adding to a losing position or doubling down after a fall, on the belief that prices must eventually bounce. Markets can instead keep falling, and a position that doubles each time can exhaust capital, margin or a firm's risk limits before the bounce arrives.
The mathematics explains why the system cannot create value. Each individual bet has the same expected return as before, and if the odds are unfavourable, as they are in a casino, doubling the stake simply multiplies the expected loss along with the stake.
For business people, the system is a useful warning about escalating commitment. Throwing good money after bad, or doubling a failing project's budget in the hope of recovery, follows the same pattern, and the discipline of cutting losses and setting limits is the antidote.
Risk managers therefore treat martingale-style behaviour as a red flag. Position limits, stop-loss rules and regular reviews exist precisely to stop a losing sequence from compounding, and good traders decide in advance the loss at which they will stop.
In practice
Real-world examples.
Example
A casino patron bets $10 on red at roulette and doubles after each loss. After six consecutive losses she has lost $630 and must bet $640 to continue, but the table's maximum bet is $500, so the system breaks down. Casinos set such limits for exactly this reason.
Example
A foreign exchange trader keeps doubling his position each time a currency pair falls. When the pair drops further than expected, his broker closes the account because he can no longer meet the margin requirement.
Example
A project manager keeps asking for double the budget each time a failing software project misses a deadline. The finance director steps in with a rule that any extension needs a fresh business case and a cap on total spending.
Formula
Calculation
Bet after n consecutive losses = Initial bet x 2^n
Total lost after n losses = Initial bet x (2^n - 1)
A trader starts with a $100 bet. After one loss the next bet is $200, then $400, then $800, then $1,600.
After five losses in a row the total lost is $100 x (2^5 - 1) = $100 x 31 = $3,100, and the next bet required is $100 x 2^5 = $3,200. If that bet wins, the trader recovers $3,200 - $3,100 = $100, which is just the original stake as profit, yet the trader had to risk $3,200 to earn $100.Case study
Seen in the real world.
Redwood Trading is an illustrative, fictional small proprietary trading firm that allowed one of its traders to double his position size after every losing trade in a particular share. For months the approach produced small, steady profits, and the trader became known for his consistency.
Then the share fell on unexpected bad news over six consecutive days. By the sixth trade the position had grown from $20,000 to $640,000, far beyond the firm's limit. With each trade losing about 10% of its size, the cumulative loss reached roughly $126,000, which is 10% of the $1,260,000 committed across the six trades, before the risk department closed everything.
The firm rewrote its policy to cap position sizes, require approval for any increase after a loss and review all strategies for hidden martingale patterns. The head of risk also began reporting the largest single position at each month-end to the partners. In this illustrative story the earlier profits had looked like skill, but they were really a slow collection of small gains that hid a rare and very large loss.
Watch out
Common mistakes.
- Believing that a long losing streak makes a win more likely, a misunderstanding known as the gambler's fallacy.
- Ignoring betting and margin limits, which make the strategy impossible to run indefinitely.
- Confusing a long run of small wins with a safe strategy, when the risk is concentrated in a rare, huge loss.
Questions
People also ask.
Does the martingale system ever work?
It wins often in the short term and can produce small, regular gains, but the occasional large loss usually outweighs them, and it cannot turn a game with negative odds into a profitable one.
Why is it called martingale?
The origin of the name is debated, and it is also used in probability theory for a different mathematical idea, which can cause confusion when people search for it.
What is a safer alternative?
Fixed or percentage-based position sizing combined with stop-loss rules keeps the loss from any single sequence limited and predictable.
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