Gin Rummy Strategy Guide
Most gin rummy decisions come down to three questions: which card to take, which card to throw, and whether to knock now or wait. The advice below draws on the classic strategy books and on computer research that tested that advice in 10,000-game matches. Every example hand was checked against the scoring in our game. If you need the basics first, start with the gin rummy rules.
Knock Early
Knock as soon as you can early in the hand. Every turn you wait gives your opponent another draw to cut their deadwood, and early in the hand the chance of drawing the exact cards you need for gin is small. One modern strategy book puts the line at fewer than ten cards discarded: below that, knock at the first chance. Older books agree; one sums it up as "when in doubt, knock."
The computer research backs this up. In 10,000-game matches between gin-playing programs, the two strongest knocked around their ninth turn on average, close to the books' ten-discard line. The bonus values matter too: with 25 points for gin and for an undercut, as in our game, the best strategies knocked mostly early in the hand, while under the older 20 and 10 bonuses they knocked far more often, including in the middle of the hand.
When to Play for Gin
Play on for gin when several unseen cards would complete your hand, and count them before you decide. Players call the count your gin chances: the number of cards that would give you gin the moment you draw one.
You could knock with 10 here, but a knock at 10 is the easiest to undercut, and nine cards are already matched with four ways to finish. The classic advice fits this hand exactly: with nine cards matched and four or more gin chances, play for gin; with only two, knock; with three, use judgment. The books also prefer playing on with seven or nine cards matched, because those hands tend to have more ways to finish than hands with six or eight.
The simulations found the books too cautious. The strongest program played for gin at more than half of its first chances to knock, with about one and a half gin chances on average, and a program built on the books' rules lost to it. The researchers' advice for human players: knock early, but from about the tenth turn, play for gin with as few as two chances.
Taking the Upcard
Take the top discard only when it completes a meld. Every card you take from the discard pile shows your opponent what you are collecting: they will stop throwing that rank and those suit neighbors, and they may hold cards to lay off on you. A card from the stock tells them nothing, and it might be a card your opponent needed.
Two exceptions earn their place. Take a discard that lowers your count enough to knock at once, and in the first couple of turns, a discard that makes a pair in a scattered hand can be worth it, as long as it is not a face card. In testing, one program that kept taking discards to make pairs after its third turn played more than 10 percent worse.
What to Discard
Throw unmatched Kings first when you know nothing about your opponent's hand. Simulations rank the King as the safest blind discard, with the Queen close behind, because high cards fit the fewest melds. A King can join only one run, J-Q-K, and a Queen two. A 7 fits three runs, 5-6-7, 6-7-8, and 7-8-9, three times as many as an Ace or a King, which is why experienced players are wary of throwing sevens.
The same logic tells you what to keep. When two cards are equally useful to you, keep the middle card: it has more ways to grow into a run. And early in the hand, do not break up a pair or a two-card run that needs just one more card, because those are your fastest route to a meld.
The safest discards of all are cards whose partners are gone. A rank your opponent has already thrown away is unlikely to help them, and so is a card whose neighbors in the suit are already in the discard pile.
Reading Your Opponent
Every card your opponent takes from the discard pile makes the same rank and the neighboring cards in that suit more likely to be in their hand. If they pick up the 8 of spades, they are probably building a set of 8s or a spade run such as 7-8-9 or 6-7-8, so hold the other 8s and the 6, 7, 9, and 10 of spades.
Their discards work the other way. If they throw the 5 of diamonds early, the 4 and 6 of diamonds become safer for you to throw, since those cards are less likely to be part of a run they are building. If they took the 9 of clubs two turns ago, throwing the 8 or 10 of clubs, or another 9, may hand them a meld.
Keep track of which cards are gone. With 31 cards in the stock at the start, every discard you remember narrows what your opponent can hold and which of your gin chances are still live.
Avoiding the Undercut
Late in the hand, knock lower or not at all. Once the stock is half gone, your opponent has usually thrown their worst deadwood, and a knock at 9 or 10 is easy to undercut, which in our game hands them the difference plus 25.
In computer tests against a simple opponent that knocks at 10, lower knocking limits won more often. A fixed limit of 4 did well against that simple opponent but was undercut more often by a stronger one, so let the limit fall gradually rather than picking one low number for the whole hand.
Turn the tables on a player who always knocks as soon as they can: hold your count down and let them knock into your undercut. Early knocks usually carry high deadwood. Our computer currently knocks as soon as it can, so a low count is your best defense against it.
Deadwood Management
Know your count after every draw. Jacks, Queens, and Kings cost 10 each, so two unmatched face cards already put you at 20, twice the knocking limit, while an Ace, a 2, and a 3 left over come to just 6.
Shed high loose cards early unless they are one card from a meld, and hold low cards as your deadwood while you wait to finish melds elsewhere. A hand that knocks with an Ace and a 2 is far harder to undercut than one that knocks with a 10. For the terms used on this page, see the gin rummy glossary, and for more common questions, the gin rummy FAQ.
Test these ideas in a free game against the computer, one hand at a time, with your deadwood shown as you play. Try counting your gin chances before every discard.
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