The Blackwood Convention (4NT) in Bridge
Asking for aces when your partnership is headed for slam
The Blackwood Convention is one of bridge's most famous tools. When your side has found a trump fit and has enough combined strength for slam (typically 33+ HCP for a small slam), the question shifts from "Can we make slam?" to "Are we missing too many aces?"
A bid of 4NT (Blackwood) asks partner to tell you exactly how many aces they hold. This prevents the disaster of bidding a slam when the opponents can cash two aces off the top.
When to Use Blackwood
Use Blackwood When
- A trump suit has been agreed (explicitly or implicitly)
- Your combined strength suggests slam (33+ HCP for small slam)
- You need to know how many aces partner has, not which ones
- You have no void in your hand (a void complicates ace-counting)
- You can handle any response without going past your safe level
Do NOT Use Blackwood When
- You have a void: Partner's ace in your void suit is worthless. Use cue-bidding instead.
- No trump fit established: 4NT after 1NT is quantitative (asking partner to bid 6NT with a maximum), not Blackwood.
- You have two quick losers in an unbid suit: Knowing about aces won't help if the opponents can cash the King-Queen of a side suit.
- The response could push you too high: If you need partner to have 2 aces and a response of "1 ace" would force you to the 6-level past your trump suit, don't ask.
Responses to 4NT
Standard Blackwood Responses
| Response | Meaning |
|---|---|
| 5♣ | 0 or 4 aces |
| 5♦ | 1 ace |
| 5♥ | 2 aces |
| 5♠ | 3 aces |
Note: After learning the ace count, the 4NT bidder can bid 5NT to ask for kings (using the same step responses). Bidding 5NT also guarantees the partnership holds all four aces.
Example Hand
Your Hand (North)
♥ K Q 3
♦ A 8 2
♣ K 4
HCP: 21 | Shape: 5-3-3-2 | Thinking: If partner has 13+ HCP, slam is likely. But are we missing two aces?
The Auction
| North (You) | South | Explanation |
|---|---|---|
| 1♠ | Open 1♠ with 21 HCP and a 5-card suit | |
| 3♠ | Limit raise: 4-card spade support, 10–12 HCP | |
| 4NT | Blackwood! Trump is agreed (spades). "How many aces do you have?" | |
| 5♦ | "I have 1 ace" | |
| 6♠ | Small slam! You have 3 aces + partner's 1 = all four. Bid 6♠. |
With all four aces accounted for, 6♠ is an excellent contract. The combined 31–33 HCP and 9+ card spade fit make 12 tricks very likely.
Blackwood vs. Gerber
A common question: when is 4NT Blackwood and when is it something else?
- After a suit has been agreed: 4NT = Blackwood (ace-asking)
- After 1NT or 2NT opening: 4NT = Quantitative (inviting slam in notrump, NOT ace-asking). Use Gerber (4♣) to ask for aces in notrump auctions.
- In competitive auctions: Context matters. Discuss with your partner.
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