When you've got the hand, you must double down

The blackjack player next to me was playing two hands at a time. The dealer had a 4 up. He was dealt a 6/4 on one hand and a pair of 7s on the other.

Doubling down on the 6/4, he bought a 3 to end up with 13. He then correctly split the 7s, catching a deuce on one 7 and an ace on the other -- so that his three hands now looked like this against that 4 up:

7/A 7/2 6/4-3

He went on to play those last two hands (on the left) the same way most people would. He just hit the 7/2 and stood with the 7/A. The dealer finished her hand, and after all the smoke cleared, the player lost three bets and won one. He then went on to lament, "Boy, if you don't make good on your double downs in this game, you're dead!"

He was right about one thing, and wrong about another. He was correct about needing to make money on your double downs to have a chance to beat the game. Where he was wrong was that all three of those hands should've been doubled!

It doesn't really matter what he or the dealer made this particular time around. The real point is, he was a solid mathematical favorite with all three hands and needed to get more money out there while holding the longer end of the gambling stick.

Yes, it's important that you make good on your double downs, but that part is largely up to Lady Luck on any given day. What's up to you, and mandatory that you do, is to go ahead and double down with every hand that you're supposed to -- bar none! Here's why.

If you play every one of your hands properly in blackjack, you'll end up winning just under 48 percent of your win/lose decisions. There's no way you're ever going to be able to win more hands than you'll lose, long term. But what percentage of all your double downs do you think you'll win? The answer is, just under 59 percent (courtesy of wizard ofodds.com)!

So if you don't double every single time you're supposed to, you're giving away the vital chance to make extra money on hands you're likely to win. That's not a winning strategy. Listed below are all 39 of your standard proper double down hands for a typical multi-deck blackjack game. If you ever let one go by, you'll just be giving the house a "pass" when you've got the best of 'em.

9 vs. a 3, 4, 5 or 6

10 vs. a 2 through 9

11 vs. a 2 through 10

A/2 vs. a 5 or 6

A/3 vs. a 5 or 6

A/4 vs. a 4, 5 or 6

A/5 vs. a 4, 5 or 6

A/6 vs. a 3, 4, 5 or 6

A/7 vs. a 3, 4, 5 or 6

One more question. Are you in the habit of doubling down with some hands not on this list? How about say, A/3 against a deuce? I see many players double with that one. It's a terrible move! If you would've just hit that hand, you'd have won it 51 percent of the time. But when you double, you won't be able to hit again if you catch an ace, 2, 3 or 8. That cuts your wins down to 48 percent -- and for twice the money!

How about doubling with say, 8 against a 5? It's actually a winning hand. Problem is, you'll win it 54 percent of the time if you just hit. But if you double, you won't be able to hit again if you catch a 2 or a 3. Now you'll win it just under 51 percent of the time. With that hand, hitting makes more money than doubling.