You’re looking at a huge hand. Partner opened 1♠, you have great spades and 18 points. Slam is likely. But if you’re missing two aces, you’re going down immediately.
You need a way to check for aces before committing to slam.
That’s what Blackwood does. One bid—4NT—asks the most important question in slam bidding: “Partner, how many aces do you have?”
Simple. Direct. And absolutely essential for any serious bridge player.
What Is Blackwood?
Blackwood is a conventional bid of 4NT that asks partner how many aces they hold.
Developed by Easley Blackwood in the 1930s, it’s probably the second-most famous convention in bridge (after Stayman). Nearly every partnership plays it in some form.
The bid is artificial—it says nothing about notrump contracts. It’s purely an asking bid about aces (and sometimes kings).
When to Use Blackwood
Blackwood works when you need one piece of information: how many aces does partner have?
You should bid 4NT Blackwood when:
1. You know slam is likely if you’re not missing two aces
You have values for slam, but you need to verify you’re not missing key controls. Blackwood tells you whether to bid slam or stop safely.
2. A trump suit is agreed (or will be obvious)
You need to know where you’re playing. If the trump suit isn’t clear, Blackwood can create confusion about the final contract.
3. You’re not worried about which specific ace partner has
Blackwood tells you how many aces, not which aces. If you need the ♦A specifically, Blackwood won’t help—you need cue bidding instead.
4. You have first or second-round control of all suits
If you have a void in a suit with no ace or king in partner’s likely holding, Blackwood can get you too high. You might be missing two tricks off the top even with four aces between you.
The Basic Responses
After you bid 4NT Blackwood, partner responds using a step system:
Traditional Blackwood Responses
- 5♣ = 0 or 4 aces
- 5♦ = 1 ace
- 5♥ = 2 aces
- 5♠ = 3 aces
The 0 or 4 aces response (5♣) is context-dependent. If partner opened 1NT showing 15-17 HCP, they’re not showing 4 aces. Use common sense.
After the Ace Response
Once partner shows aces, you decide:
If you’re missing two aces:
Stop at 5 of your trump suit. Don’t bid slam.
If you’re missing one ace:
Bid your small slam (6 of the trump suit).
If you’re missing zero aces:
You can ask for kings by bidding 5NT (see Advanced section below). Otherwise, bid 6 or consider 7.
Example Hands
Example 1: Safe Slam
Your hand:
♠ AKJ1072 ♥ K3 ♦ AQ5 ♣ K4
HCP: A=4, K=3, J=1, K=3, A=4, Q=2, K=3 = 20 HCP ✓
Partner opens 1♠. You have 20 HCP, six spades, and strong controls. Slam is likely.
Auction:
Partner You
1♠ 4NT (Blackwood — how many aces?)
5♥ 6♠ (2 aces! We have all four — bid slam)You’re not missing any aces. 6♠ is safe.
Example 2: Stop Short
Your hand:
♠ KQJ52 ♥ AK ♦ KQ83 ♣ A7
HCP: K=3, Q=2, J=1, A=4, K=3, K=3, Q=2, A=4 = 22 HCP ✓
Partner opens 1♠ showing 13+ points. You have 22 HCP and great spade support. But you need to check aces.
Auction:
Partner You
1♠ 4NT (Blackwood)
5♦ 5♠ (1 ace — we're missing two — stop at 5♠)Partner has 1 ace. You have 2. That’s only 3 total—you’re missing an ace. Don’t bid slam.
Example 3: Asking for Kings
Your hand:
♠ AKQJ2 ♥ AK ♦ AQ5 ♣ K73
HCP: A=4, K=3, Q=2, J=1, A=4, K=3, A=4, Q=2, K=3 = 26 HCP ✓
This is a powerhouse. Partner opens 1♠. Grand slam is possible if partner has the right kings.
Auction:
Partner You
1♠ 4NT (Blackwood — aces?)
5♥ 5NT (2 aces! Ask for kings)
6♦ 6♠ (1 king — not enough for grand slam — stop at 6♠)After confirming all aces are present (you have 3, partner has 1, or you have 2 each), you asked for kings with 5NT. Partner showed 1 king. Not enough for a grand slam, so you stopped at 6♠.
Example 4: When NOT to Use Blackwood
Your hand:
♠ AKQ65 ♥ 7 ♦ KQJ84 ♣ A6
HCP: A=4, K=3, Q=2, K=3, Q=2, J=1, A=4 = 19 HCP ✓
Partner opens 1♠. You have great values, but there’s a problem: you’re weak in hearts.
Auction:
Partner You
1♠ ???Don’t bid 4NT here.
Why? Blackwood tells you how many aces partner has, not which aces. If partner shows 2 aces with 5♥, you still don’t know if they have the ♥A.
If they don’t, the opponents can cash two heart tricks immediately.
Instead, use cue bidding to show controls and find out specifically about hearts.
When NOT to Use Blackwood
This is as important as knowing when to use it.
1. When you have a void
If you have a void and partner shows an ace in that suit, it’s “wasted.” You’re counting four aces but actually missing a critical control elsewhere.
2. When you need a specific ace
Blackwood tells you how many, not which. If you need the ♦A specifically, cue bid instead.
3. When partner might have no aces
If you bid 4NT and partner shows 0 aces (5♣), you’re already at the 5-level with no escape. Make sure slam is still reasonable even if partner has zero aces.
4. When trumps aren’t agreed
If you don’t know what suit you’re playing, 4NT creates confusion. Agree on trumps first, then use Blackwood.
5. When opponents are interfering
If RHO overcalls your 4NT bid, the response structure gets complicated. Many partnerships have agreements for interference, but if you don’t, avoid Blackwood in competitive auctions.
Advanced: The 5NT King Ask
After partner responds to 4NT, you can bid 5NT to ask for kings.
Requirements for 5NT:
- You’ve already bid 4NT and heard partner’s ace response
- You’ve confirmed you’re not missing two aces (you’re already committed to slam)
- You’re considering a grand slam
King responses (same structure as ace responses):
- 6♣ = 0 or 4 kings
- 6♦ = 1 king
- 6♥ = 2 kings
- 6♠ = 3 kings
Note: Bidding 5NT commits you to slam. If you bid 5NT, you’re promising you have all the aces and are looking for grand slam. Don’t bid 5NT and then stop at 5.
When 4NT Isn’t Blackwood
Not every 4NT bid is Blackwood. Here’s when it’s NOT Blackwood:
1. When no suit is agreed and notrump was bid naturally
1NT - 4NTThis is a quantitative raise, inviting 6NT. It’s not asking for aces—it’s asking partner to bid slam with a maximum.
2. After interference
(4♠) - 4NTThis is typically for takeout, not Blackwood. You’re showing a big hand and asking partner to choose a suit.
3. When it would commit you beyond a safe level without knowing the answer
Partnerships often have specific agreements about when 4NT is Blackwood vs quantitative vs something else. Discuss this with your partner.
Common Mistakes
1. Using Blackwood with a void
You have a void in hearts and 3 aces. Partner shows 1 ace with 5♦. Is it the ♥A (wasted) or a useful ace? Blackwood can’t tell you.
2. Using Blackwood when you need a specific ace
“I need the ♦A or we’re going down immediately.” Blackwood won’t tell you which ace partner has. Use cue bidding instead.
3. Bidding 5NT without all the aces
5NT commits you to 6. Don’t bid it unless you’re sure you have all four aces.
4. Forgetting that 5♣ can mean 4 aces
Context matters. If partner opened 2NT, they might actually have 4 aces. Don’t assume 5♣ always means zero.
5. Using Blackwood too early
Make sure slam is actually likely before you start asking for aces. If you’re not close to slam values, save Blackwood for when you actually need it.
Modern Variations
Roman Key Card Blackwood (RKCB):
Treats the king of trumps as a fifth “ace” (because it’s equally important in many slams). This is the modern standard for serious partnerships.
1430 vs 3014:
Different response structures for RKCB. Discuss with your partner.
Exclusion Blackwood:
A jump to 5 of a suit (above 4NT) asks for aces excluding the bid suit. Used when you have a void.
These are advanced. Learn basic Blackwood first.
Why Blackwood Matters
Slams are exciting. They’re also risky.
Bidding 6♠ and making it is worth 1430 points (vulnerable). Bidding 6♠ and going down because you’re missing an ace costs you -100 (or -200 doubled).
Blackwood is your safety check. It keeps you out of bad slams and helps you get to good ones.
Master it, and you’ll bid slams with confidence instead of hope.
Partnership Agreements to Discuss
1. When is 4NT Blackwood vs quantitative?
After 1NT-4NT, is it asking for aces or inviting slam? Standard: it’s quantitative. But discuss.
2. Do we use RKCB or regular Blackwood?
RKCB is more powerful but requires partnership agreement. Make sure you’re on the same page.
3. What if opponents interfere over 4NT?
Do we use DOPI, DEPO, or something else? (Don’t worry about this yet if you’re a beginner—just know you’ll need an agreement eventually.)
4. When does 5NT ask for kings?
Standard: always. But some partnerships use 5NT for other purposes (specific king ask, grand slam force, etc.). Clarify this.
Want to practice Blackwood in real auctions? Try Brian, our AI bridge coach, and get instant feedback on when to use (and when to skip) Blackwood in your slam bidding.