Calculating Odds and Outs; Part V; Bet sizing, and Expressed verses Implied Odds

by ~ May 15th, 2008. Filed under: Instructional posts.

* Modified June 15th, 2010 *

I’m finally just about ready to wrap this up. As usual, it was more work than I expected and took more words and more posts than I had anticipated.


Bet sizing

We’ve looked at when to call bets relative to your draws, and I mentioned briefly how terrible small bets are since they give anyone with draws the proper odds to call. We need to look at the other side; how to size your bets so as to give you opponent the incorrect odds to call.

Essentially this is just the inverse of pot odds calculations.

You are in the big blind. One limper calls $10, the small blind folds. You check your K9 and the flop comes K65. You have top pair with a so-so kicker. Immediately you should see that there is a spade flush draw as well as possible straight draws with the 65. If you bet too small, you will give your opponent the correct odds to call. You know the flush draw is 4.2 to 1 to hit on the turn, and the open ended straight draw is 4.9 to 1. The flush draw has better odds, so if you give the flush draw incorrect odds you will also give him incorrect pot odds in case he has the OESD.

How much do you bet to make it incorrect for your opponent to call if he has a flush draw? The pot is $35. A standard bet here would be 1/2 pot, so bet $20. If you do so, the pot becomes $55 and your opponent has to put in $20 to continue. This means he has 55/20 odds, or 2.75 to 1 odds, not enough for either the flush draw or the straight draw. What if he happens to have the flush draw and one card is the A? That gives him 12 outs, requiring 2.9 to 1 odds; still not enough.

What about the if he’s holding the 78? In that event he has 9 flush outs plus three 4s and three Ts for 15 outs and 2.1 to 1 odds to continue. To make it incorrect for him to call, you have to bet the pot, $35, to give him $70 to $35 odds or 2 to 1. In reality it’s very unlikely that this or some other straight/flush combination this strong is what he is holding, and if so he’s probably not going to fold no matter how much you bet.

Notice that the larger you bet, the larger the pot becomes, but that the ratio of the pot odds does not increase as fast as you increase your bet size is increasing. A 10% pot sized bet gives off 11 to 1 odds, a 50% pot sized bet gives 3 to 1 odds, but a 100% pot sized bet only brings the odds down to 2 to 1.


Other factors

There’s more to playing poker than odds. Some to consider include:

  • stack sizes relative to pot sizes – ie. if on the flop your stack size is not much larger than the pot, just push all in because you won’t have enough left to bet at the turn or river anyways
  • bubbles in tournament settings – the balance between aggression and survival is more important than pot odds
  • fold equity, semi-bluffing your draws – especially out of position it can be a better option to bet into your opponent rather than waiting to see what odds they will give to to chase your draw
  • opponent reads – if your opponent bets at most flops, you can happily call with your draws (or raise them) even if you’re not getting correct pot odds simply because there’s a good chance he has nothing


Expressed odds and Implied odds

What we’ve looked at so far come under the heading of “expressed odds”; numbers based on the bets, card odds and pot sizes. Lets say you have 98 and the flop is A76. The pot is $35, and your opponent in the big blind bets $20 making the pot $55. You are getting 55 to 20 pot odds, or 2.75 to one. Your open ended straight draw has a 4.9 to 1 chance of hitting on the turn. Fold?

But say you called and the turn is a Ten. You’ve made the straight. Now you’ve got the turn and the river to make more money from your opponent. Or, say the turn is a 5 of some kind. A 5 is a little more obvious since it gives a 567 on the table, so maybe you won’t be able to get quite as much money from your opponent.

This extra money that you collect when you hit your hand is what is referred to as “implied odds”. Implied odds are very imprecise, but very real, odds that you will collect money when you hit your draw. But, they are affected by

  • the size of your and your opponents’ stacks
  • the “hiddenness” of you hand
  • your opponents’ hand
  • your opponents’ abilities

If either your stack or your opponents’ stack is small, then the implied odds are limited since you will not be able to collect very much if you hit your draw. Implied odds are not often a factor in a one table Sit and Go because the starting stack sizes are shallow (not many big blinds). They are definitely a factor in playing full buy-in cash games, and may be a factor in multi table tournaments and deep stack tournaments as well.

If your draw is obvious, like a flush draw, your opponent may be hesitant to pay you off if the flush fills. On the other hand if you hold 86 on a T74 flop and a 9 or a 5 hits it’s much less obvious that you had two straight draws and you may get a big payoff.

If your opponent has a weak hand, he may fold when you bet or raise on the turn or river simply because he doesn’t see the point of defending a weak hand even if he’s not sure what you have. If your opponent has flopped a set or other big hand, you may be able to get his entire stack if your draw hits.

If your opponent is not good or is unable to back down to aggression, you may be able to get his stack regardless of how strong his hand is if you hit your draw. If your opponent is good, he may be able to lay down his top pair or overpair if he suspects that you’ve hit your draw.

I think one of the toughest things about playing low level micro stakes is trying not to give off big implied odds. You make a good sized bet at the flop, at the turn, and the flush fills on the river and your opponent bets into you. Did he make the flush? Does he even understand pot odds? Or is he betting because the flush is a good scare card to bet? Or did he make a second pair with the river card? Or was he slowplaying his set that he made on the flop? Any of these are possibilities.


One more related term; reverse implied odds. That applies when a big stack opts to play against another big stack with a hand that is easily dominated. If you can’t fold these types of hands you give off reverse implied odds. See this post for an example.


That’s it for now. I’ll probably come back and make revisions and clarification. Email if you have questions or spot a mistake.


The rest of the series:


Compendium of instructional posts:

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