What happens if you run out of time in chess?

You lose, under Article 6.9, but with one exception that saves plenty of players: if your opponent could not checkmate you by any possible series of legal moves, the game is a draw instead. So if you have nothing but a king and your opponent has a king and a knight, your flag falling is half a point; if they still have a rook, it is zero.

Can a chess game go on forever?

No. Article 9.6 stops it: as soon as the same position has appeared five times, or seventy-five moves have gone by with no capture and no pawn move, the game is drawn on the spot, whether or not either player says anything. The claimable versions of those rules, at three repetitions and fifty moves, come into play long before that.

Do you have to checkmate to win a chess game?

No. Most games between strong players end in resignation, because a player who is a rook down with no compensation already knows how the rest goes. Below club level, resigning early is usually a mistake: at 1000 rating, opponents give material back often enough that a lost position is worth playing on.

How does a chess game end?

Nine things can stop a chess game, and only three of them hand somebody the whole point. Beginners tend to know one of the nine, which is how you end up with an 800-rated game finishing in a draw that one player did not want and the other did not know they had just earned.

The three ways to win

Checkmate is the first, and it is the only ending that needs no agreement from anyone. The king is attacked, there is no move that stops the attack, and the game is over that instant under Article 5.1 of the FIDE Laws. Nobody plays on, nobody captures the king.

Resignation is the second, and it is how most master games actually stop. You tip your king over or you offer a handshake and say the word. Article 5.1 again, and it takes effect immediately: how to resign covers the etiquette, though at beginner level my advice is to do it far less often than you feel like.

Time is the third. Your flag falls, you lose, under Article 6.9. One exception matters: if the player still on the clock could not checkmate you by any series of legal moves, it is a draw rather than a win, so a king and a knight against your lone king gets nothing when you flag. That is what happens when your time runs out.

The six ways to draw

Stalemate: the player to move has no legal move and is not in check. Half a point, and it has rescued more lost positions than any other rule. Read what stalemate is before you try to win an endgame with a queen.

Agreement: one player offers, the other accepts, and it is over. Offer after you move and before you press the clock.

Threefold repetition: the same position, with the same player to move and the same possible moves, turns up three times. Article 9.2, and you have to claim it. Perpetual check is this rule wearing a hat.

The fifty-move rule: fifty moves by each player with no capture and no pawn move. Article 9.3, and again you claim it.

A dead position: neither side can ever deliver mate, so play stops at once. The everyday case is insufficient material, a king and one bishop or one knight against a bare king.

King and bishop against a bare king. No arrangement of these three pieces is checkmate, so the game is drawn the moment the last pawn comes off.

And the automatic pair. Article 9.6 draws the game with no claim at all once the same position has occurred five times or seventy-five moves have passed without a capture or a pawn move. Those exist so nobody can sit there repeating forever.

Three things that feel like an ending and are not

Losing every piece except the king does not end anything. You keep playing, and a lone king can still stalemate its way to half a point.

Being in check does not end anything either. You have three ways out and you must use one of them.

Nor does a draw offer. Refusing is free, it costs you nothing, and there is no limit on how many times your opponent may ask, though repeatedly pestering someone about it is a matter for the arbiter.

If it is the drawing half you want in detail, every one of those six has its own page under draws. If it is the winning half, start with the mate you will actually get to play: mate in one.