Losing streaks: how long a cold run gets, worked out

Every bettor meets a cold run, and the instinct is to read it as news: something stopped working, the luck turned. The arithmetic of streaks says it's usually neither. Long runs of losses are what a long sequence of bets looks like.

The odds of a losing streak

Treat each bet as independent, with the same chance of winning every time. The chance of at least one losing run of a given length or longer, somewhere in a sequence of bets, can then be worked out exactly. Over 500 bets:

• At a 55% win rate: a run of 7 straight losses, 64.4%. Of 8, 36.9%. Of 10, 8.8%.
• At 52.38%, break-even at −110: 7 losses, 77.0%. 8 losses, 50.0%. 10 losses, 14.4%.
• At 50%: 7 losses, 86.4%. 8 losses, 62.5%. 10 losses, 21.5%.

The longest losing run in a typical 500-bet stretch — the median — is 7 at a 55% win rate, 7 at break-even and 8 at 50%. A good bettor and a losing one share most of the same streaks.

Over a season instead of a career

Fewer bets means shorter runs, not none. Over 100 bets at 55%, there's a 17.9% chance of seven straight losses and a 64.7% chance of five. Over 1,000 bets, the same bettor sees a run of ten 17.0% of the time.

What a streak costs

A streak is counted in units, so the unit decides what it costs. At a flat 1 unit a bet, ten straight losses cost 10 units: a tenth of a 100-unit bankroll, a fifth of a 50-unit one. At half a unit a bet, the same streak costs half as much. Which unit fits a bankroll is your call; the bankroll calculator shows what a cold run does to the one you set.

Why a streak says little

A 55% bettor and a 50% bettor both hit long runs, so a streak can't tell them apart, and neither can a short record. Going 22–18 proves nothing. Demonstrating a real 55% takes about 2,200 bets.

Bankroll Guardian is a bet-tracking and analytics tool — not a sportsbook, and none of this is betting advice. Betting carries risk; please bet responsibly.