Analyzing Double Down
Let's take a closer look at why double down is such an effective player option. To do so, we are going to analyze just one possible hand — in this case, a player's 5 and 4 (point total 9) against a dealer's up card of 5.
If you were to put this hand to statistical analysis using blackjack simulation software, you would come up with the following:
Hitting it would result in your winning 59 times out of 100.
Doubling down would make you a winner 57 times out of 100.
In other words, you stand to lose two more hands by exercising the double down option than if you decided to just hit the hand. You might be thinking that 2 percent, or two hands, really doesn't make that much of a difference. Or does it? Actually, it does.
Let's say you're betting $10 a hand. In the first scenario, you would win $590 and lose $410, for a net profit of $180. Not bad, right? But you can do better! Now, suppose you doubled down and increased your bet to $20. You would win $20 fifty-seven times, for a total of $1,140, and you would lose $860, for a net profit of $280. That is an extra $100, even though you lost two more hands.
Now that 2 percent doesn't seem so insignificant, does it?
Doubling down will not improve your chances of winning a hand. For this reason, the frequency of winning a hand doesn't determine whether you should double down. In fact, you should expect to lose a bit more often when you double down. So don't let the fact that you'll lose more hands govern your double down decisions. Instead, consider how much you stand to gain if you do double down and win.

