What is an undercut in gin rummy?

The undercut is what stops gin rummy from being a race to knock first. Knock carelessly, and your opponent can flip the whole hand against you.

Quick answer: An undercut - also called an underknock - happens when the player who did not knock ends up with deadwood equal to or lower than the knocker's. Instead of the knocker scoring, the defender scores the difference plus a 25-point bonus. It's the penalty for knocking when your opponent was just as low.

How an undercut works

When you knock, your opponent lays off and counts their deadwood. If their total is equal to or lower than yours, they've undercut you. Rather than you scoring, they score the difference between the totals plus a 25-point bonus. Knock with 9 while they finish on 6, and they collect 3 plus 25.

Why it changes strategy

The undercut is why a knock isn't free. Knocking the instant you hit ten deadwood is risky if your opponent looks close to going out. Skilled players knock low - with a small deadwood total - or knock early before the opponent can get set, precisely to dodge the undercut. Going gin avoids it entirely, since no one can tie zero.

Reading the risk

Judging undercut danger means watching what your opponent draws and discards. If they've been taking cards from the discard pile and throwing little away, they may be nearly melded - a bad moment to knock high. Our strategy guide covers reading these signals.

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Related questions

What does it mean to knock in gin rummy?

Knocking ends the hand. You may knock the moment your unmatched cards - your deadwood - total ten points or fewer. You lay down your melds and your deadwood, your opponent lays off what they can, and the player with the lower deadwood scores the difference. Knock too greedily and you risk being undercut.

How is gin rummy scored?

When a hand ends, the knocker scores the difference between the two players' deadwood totals. Going gin adds a 25-point bonus (and the opponent can't lay off). If the defender ties or beats the knocker, that's an undercut, worth the difference plus a 25-point bonus. Match bonuses reward winning the game and each hand.

What is a good gin rummy strategy?

Strong gin rummy comes down to a few habits: watch what your opponent draws and discards, hold low and flexible cards while shedding high unmatched ones, avoid discarding cards your opponent can use, and knock with a low deadwood total to dodge an undercut. When in doubt, take the safe, early knock.