# Doubling on Blackjack

#### antibes

##### Dormant Account
Does anybody know what the rate of winning is when you double up on Blackjack using WoO strategy tables.

If it is only 50/50 I don't see the point of ever doubling.

I calculated this some time last year and posted the results here.

The probability of winning is usually 50%-60%, the probability of a tie is around 10%.

antibes said:
If it is only 50/50 I don't see the point of ever doubling.
If it were, you wouldn't.

I once did a very extensive manual run using D9 rules, and got 60/40 in favour. Factoring in soft doubles, it's probably about 56/44.

BTW, on the subject of BJ theory: check out the BJmath website. My estimation of them has just gone through the floor - they're advertising Golden Palace:

This casino has a 300% bonus and good statistical odds. Test your strategies online."

Bah, gimme a break. These people should be setting an example. How about putting up one of the REPUTABLE casinos on the homepage? Intercasino? iNetbet? 32Red?

Jeez.

out of interest what are the odds for the following

11v5
11v6
10v5
10v6

also if any can oblige what are the odds of the dealer drawing to 20/21 when starting on 5/6

I have never liked doubling on soft Aces but do according to the chart.

So if I ignored them, and just doubled on 9, 10 or 11 it wouldn't make much difference then.

antibes said:
I have never liked doubling on soft Aces but do according to the chart.

So if I ignored them, and just doubled on 9, 10 or 11 it wouldn't make much difference then.

You're giving up about .1% when you don't double any soft totals. So about a \$1 loss per \$1000 wagered. (Based on the wizards Blackjack house edge calculator)

Doesn't seem like much. But when you're playing a game with a .4% HA, you're increasing the house edge by over 25% when you don't double your soft totals.

scrollock said:
out of interest what are the odds for the following

11v5
11v6
10v5
10v6

Probability of win/tie/loss
11v5 0.621849, 0.0699025, 0.308249
11v6 0.635285, 0.0666062, 0.298109
10v5 0.596309, 0.0709274, 0.332764
10v6 0.612106, 0.0680937, 0.3198

scrollock said:
also if any can oblige what are the odds of the dealer drawing to 20/21 when starting on 5/6
or
.

How on earth can you be so accurate with the odds!

Different subject - splitting 8s.

I cannot see the advantage of splitting 8s when the dealer has 10 or A, or even 9.

I hit being 16 as most times I was losing 2 bets when I split.

antibes said:
How on earth can you be so accurate with the odds!
No secret. All these numbers are listed in the BJmath glossary.

antibes said:
I cannot see the advantage of splitting 8s when the dealer has 10 or A, or even 9.
You lose less. Two eights as the initial card beat the hell out of one hard 16, whatever the dealer's showing.

caruso said:
No secret. All these numbers are listed in the BJmath glossary.
Can you give me a link? I have calculated the numbers myself. I should have mentioned that they are for 8 decks, dealer stands on soft 17.

caruso said:
You lose less. Two eights as the initial card beat the hell out of one hard 16, whatever the dealer's showing.
The two 8's aren't exactly great either. The possible decisions in the order of decreasing expected value are: split, surrender, hit, stand and double, and there is not much difference between the first four. The point is that it does not matter whether your moves have positive or negative expected value, you should make the one with the highest expected value, even if it just means that you expect to lose less than with the other choices. Some of the soft doubles mentioned earlier are not particularly great either, but doubling in those situationd is better than hitting or standing.

Tks for the replies.

So it is best then to stick exactly to the WoO chart.

I use the basic chart if I don't know what software they are using. Does that matter much?

The software doesn't matter, it's the rules that dictate what strategy chart is optimal.

The key rules are

Whether the dealer hits or stands on soft 17 (it's worse for you when the dealler hits)

Can you double after splitting (you split less often when you can't double)

Can you double on 10/11, 9/10/11, or any 2 cards.

Can you surrender.

Does the dealer peek for blackjack. The key here is whether you lose multiple bets if you double/splilt and the dealer has blackjack. If the dealer doesn't peek, but you get any double/split bets back, then you can treat the game as if the dealelr is peeking.

GrandMaster said:
Can you give me a link?

Those are only expected value tables, they don't give the probabilities of the various outcomes. The can calculate the expected values from the probabilities, but not the other way around.

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