There are times when you should semi-bluff and times when you shouldn’t. To semi-bluff or bluff successfully then you need your opponent to fold some of the time. Let us say that your opponent made it 3.5bb to go and you called on the button with both blinds folding. The pot is now 8.5bb and your opponent makes a c-bet of 5.5bb making a 14bb pot. Now if you semi-bluff or bluff with a drawing hand then you may raise to something like 18bb. This makes the pot 32bb of which 18bb of those are yours in this current play.
This means that your opponent needs to fold more than 56% of the time for the play to show immediate profit. This is because that is the amount of the money that you have places into the pot on this one play. Forget about any money that you placed pre-flop because that money is gone. So to have some sort of overlay in this situation then we need our opponent to fold more than 60% of the time but how can we know how often they will fold to a bluff raise?
Well luckily there is a simple answer and that answer is how wide your opponents range is and how much of that range they will fold to aggression. Let us say that the flop is 10s-7d-4d and your hand is the Jh-8h. If your opponent only ever held aces down through queens then any raise that you made on the flop would likely have zero fold equity. This is for the simple reason that our opponent has only strong hands in their range. They would doubly not fold to a flop raise because the board also has drawing possibilities.
Our fold equity is clearly then linked with the width of our opponents range and how many hands are in that range. Let us add a new range where we placed seven hands into that range where our opponent would fold to our bluff raise. Clearly against this play then we would have 100% fold equity but this wouldn’t be representative of real life play because our opponent wouldn’t have weak hands all the time. However if we merged those seven hands with the three strong hands then we can see that our opponent would fold 70% of the time.
What this means is that we can now bluff raise profitably even if we have no equity. If our opponent folds 70% or more and we only need them to fold more than 56% of the time then we have a clearly profitable play. This works even better if we have outs because even if we raise and get called then we will sometimes make the best hand and extract more value from that. So let us compare the range of an UTG raiser with that of a cut-off raiser. An UTG raiser in say six max may be raising with 15% of their hands while a cut-off raiser could be raising with 35%.