Quote Originally Posted by Dummy View Post
Can someone help me understand why my math doesn't work with this strategy?
Using basic blackjack strategy, bets would follow a grand martingale (1, 3, 7, 15, 31), except that if the bet of 31 is lost, the betting starts over at 1. Now based on googling, there is a 2.8% chance of losing 5 hands in a row or a 2.8% chance of losing the bet of 31. That would mean 97.2% of the time, I would win 1. The expected value of this is about .1 profit per hand and assuming a large enough bankroll, will this not be profitable in the long term? What am I missing? I tested this on a few online sites and have profited quite a bit.
Dummy,

When you lose five in a row, you don't lose just 31 on the streak: you actually lose 1 + 3 + 7 + 15 + 31 = 57.

Let's try the math this way. For typical BJ rules, Basic Strategy gives an EV of about -0.5%, or -0.005 (give or take a bit due to house rules). This means that when you place a 1-unit bet, on average you'll lose 0.005 units. Similarly, when you place a bet "b" of 3, 7, 15, or 31 units, on average you'll lose 0.005*b. This means that, on average, no matter how much or little you bet, you'll lose 0.005 times whatever you wagered.

Hope this helps!

Dog Hand