[Knurdler]

We know that 1N 4N or 2N 4N is a quantitative bid asking opener to bid 6 if max and pass if min.
I believe the idea is to end up in 6N if we have 33 points, because with 33 we cannot be missing 2 aces.

Question 1: What I have never grasped is why the total point target is 33 and not 34? 33 leaves 7 for the opponents, which could be and an ace and a king.

Question 2: when is 4N quantitative? What I can find says:
1. after a natural NT opening – I am happy with that.
2. After a natural NT reply eg 1D 3N 4N – sounds reasonable
3. If the bidding started NT and a suit has not been agreed – sounds reasonable
4. What about after openers NT rebid eg 1m 1M 1N 4N or 1m 1M 2N 4N? (Just in case it is relevant, we do play checkback).

Question 3: if 1 of us knows we have 33 or more combined points and 4NT is quantitative, how do we check how many aces we have? Yesterday partner opened 1C with 21 and I replied 3N showing 13 to 15 with no 4cm (a bid we rarely use). He bid 6N. With 4 aces and 4 kings, we made 13. Putting aside that he might have opened 2C, how would he ask me about aces?

I have read the 2025 Topic by WTRCLR.

Thanks

[DavidKok]

To the point: I play quantitative NT in many situations. Instead I list when 4NT is Blackwood.
Many players, in my experience especially weaker players, love love love bidding 4NT to use their ace asking gadget. In my opinion this is a terrible habit.

On the example auction I think the 3NT bid is very unwelcome. You are preempting partner and taking away almost all bidding space. No wonder there's compromises after! Even if your bid shows exactly 3=3=3=4 13-15 I think it's a system flaw.

Slam bidding relies heavily on hand evaluation and exchanging information. If you want to improve your slam bidding, look for the bid that consumed your bidding space. Usually that's the reason you couldn't explore something later. If you try to change your 4NT information without addressing the earlier jump you're not really moving the needle.

[pescetom]

I would add that the 33 target is not written in stone (it can be quite right to call 6NT with less, but knowledge about running suits) and not so much about missing precisely A and K in different suits but in assuring that sufficient control is present overall to lose only one trick.
As a corollary, it is not particularly important to know the number of Aces (except when holding exactly 32 and feeling pessimistic) nor is holding all four any good reason to prefer 6NT to 4NT.
Far too many people ask Aces as a way to "decide" when unsure whether they have enough for slam or not (perhaps even sacrificing a quantitative enquiry to do so). Often they then make a seat of pants decision after the predictable discovery that one Ace is missing.

[Zelandakh]

Since this is N/B I think it's best to keep it simple. 4NT is quantitative if:
1. Partner made a natural NT call and we are unlimited
2. We have a way of making a forcing raise and quantitative makes sense
3. any specific situations you agree with your partner

As for 33hcp, the reason for this has nothing to do with aces. Rather 32-33 points has proven to be the break-even point for slam being a good bet between 2 balanced hands from experience and simulation. Even if the missing 7 points are an Ace and a King, the chances of them being in the same suit are low and of being specifically in Opening Leader's hand even lower. This often gives Declarer practical chances of rounding up 12 tricks in the other 3 suits before the opponents can take their 2, even when Double Dummy analysis says the slam is bad.

Finally, the number of aces you hold in NT auctions is usually less important than your general strength. If the key piece of information you need before bidding slam is in fact the number of aces, the simple way of doing this is by setting a suit as trumps and only then using some variety of Blackwood. Notice the point here though - you need to answer the specific question "Are we missing 2 aces?" or, with slightly more advanced methods "Do we hold specific cards for a grand slam?". You do not use Blackwood (with the specific exception of Conditional Key Card Blackwood, an advanced convention) for finding out whether you hold enough strength for slam. For that, there are much better options available.