Bankroll and risk of ruin

A counter with an edge and the wrong bet size still goes broke. Hand-to-hand swings are a hundred times the size of a 1% edge, and risk of ruin is the probability those swings zero you out before the long run arrives. It depends on two things you control: your edge and your bet size relative to your bankroll.

Size the game by its maximum bet, not by the unit alone. In the taught 1-to-8 spread, max bet equals unit × 8. A unit that sounds small can therefore put a large share of the bankroll on the table at the best counts. Keep your largest bet near 1% of bankroll, then use the betting calculator for your exact game.

The old '1% unit' rule assumed a flat bet with no spread. Once you spread, it does not apply. In the calculator's model for Hi-Lo, the taught 1-to-8 spread, and default rules, a 1% unit means an 8% max bet and about 77% lifetime risk of ruin. Even 0.5% units have about 60% ruin, while 2% units reach about 88%. To get ruin near 15%, the unit has to be near 0.13% of bankroll, which puts the maximum bet near 1%.

For a $2,000 bankroll, practical sizing is a $2.50 unit and a $20 maximum bet, not a $25 unit. The exact 0.13% calculation is $2.60, so $2.50 rounds down to a bet you can actually place. If the table minimum will not accept that unit, the bankroll cannot support the taught spread at that table.

A solo counter's long-run win rate is roughly one unit per hour of good conditions, through swings that include losing weeks and the occasional losing month. A hot night does not justify raising the unit, and a cold night does not justify chasing. Neither changes the math. Bet the same unit either way.

The bankroll is separate money, fully committed before you play, and you never chase a session loss. Do not top it up mid-trip from the checking account. If losing the whole bankroll would hurt, the correct bet is zero. To get hourly EV, standard deviation, and risk of ruin for your exact bankroll, unit, spread, and rules, use the betting calculator on this site.