How Does a Chess Clock Work?

A chess clock is two clocks joined together so that only one of them can ever be running. When it is your turn, your time counts down. You make your move, press the button on your side, and that single action stops your clock and starts your opponent’s.

That is the whole mechanism. Everything else — increments, delays, flag falls, the button you must press with the correct hand — is detail built on top of it.

If you already know all this and just need to set one, we have quick-start guides for thirteen common clocks.

What is a chess clock for?

To stop games lasting forever, and to make thinking time part of the contest.

Without a clock, a losing player can simply refuse to move. With one, time is a resource you spend like any other: you can pour twenty minutes into one critical position, but you will pay for it later. Learning to spend it well is a real chess skill, and one most players are worse at than they think.

Every rated game — club championship, league match, weekend congress — is played with a clock.

How do you use a chess clock?

The sequence never changes:

1. Make your move on the board.
2. Press your clock, using the same hand you moved with.
3. Your clock stops. Your opponent’s starts. It is now their problem.

Four rules catch people out, all of them from the FIDE Laws of Chess:

• Move first, then press. Pressing the clock before moving is explicitly forbidden (Article 6.2.4), along with pressing it forcibly, picking it up or knocking it over.
• Same hand. You must press with the hand you moved the piece with (Article 6.2.3) — no moving with your right and slapping the clock with your left. You also may not rest a finger on the button or hover over it. Moves themselves must be made with one hand only (Article 4.1).
• The gap is your time. The seconds between putting the piece down and pressing the button come out of your clock, not your opponent’s (Article 6.2.2).
• Nobody will remind you. An arbiter is specifically instructed not to tell a player that they have forgotten to press their clock (Article 12.6). If you walk away without pressing, your time simply drains.

At the start, White’s clock is started (Article 6.6) — before White has done anything at all.

What happens when the flag falls?

“Flag-fall” means your allotted time has run out. The name is a leftover from mechanical clocks, where a small metal flag was nudged up by the minute hand and dropped as it passed twelve. Digital clocks have no flag; the term stuck.

If your flag falls, you lose — with one important exception. Article 6.9:

if a player does not complete the prescribed number of moves in the allotted time, the game is lost by that player. However, the game is drawn if the position is such that the opponent cannot checkmate the player’s king by any possible series of legal moves.

So if you run out of time while your opponent has nothing left but a lone king, the game is a draw, not a loss. They could not have mated you however the game continued, so your clock running out costs you only the half point.

Somebody has to notice

This is the part that surprises club players most. A fallen flag does not end the game by itself. Article 6.8:

A flag is considered to have fallen when the arbiter observes the fact or when either player has made a valid claim to that effect.

In a standard-play game, if your opponent’s time expires and neither of you notices, play simply carries on — and if your flag then falls too, you have thrown away a win you already had. Watch both clocks, not just your own.

Rapidplay works differently: there the arbiter is directed to call a flag fall if they see one.

Increment and delay

Modern controls give you time back. Increment adds a fixed number of seconds to your clock every time you press it — at 15+10 you begin with 15 minutes and earn 10 seconds a move, so you can never be left with literally no time to move. It is sometimes called Fischer increment, after Bobby Fischer, who patented a clock that did it.

Delay is the other approach, and more common on American clocks. Instead of adding time, it waits: your main time only starts counting down once the fixed delay has elapsed (Article 6.3.2). Press within the delay and you lose nothing, but you never bank the surplus either.

British and FIDE events almost always use increment. Our chess clock hub has the notation explained and a table of the controls clubs actually play.

Where does the clock go on the board?

In a formal event, the arbiter decides before the game starts (Article 6.5) — it is not the players’ choice, and not Black’s, despite that being widely repeated.

In practice arbiters put it on the same side throughout the hall so results can be read at a glance, and club games follow whatever the room has settled on. If it is genuinely awkward — a left-handed player facing a clock placed for a right-hander — ask rather than move it yourself.

Analogue or digital?

Analogue clocks are the two-dial mechanical sort with the physical flag. They cannot do increment or delay, which is why they have all but vanished from rated chess. Plenty still work perfectly well for casual games.

Digital clocks handle increment, delay, multiple time periods and move counters. Any clock used for a rated game today will be digital.

What clock do tournaments use?

DGT, more often than not. The Dutch manufacturer has produced the “Official FIDE Chess Clock” under an endorsement from FIDE since 1993, and the DGT 3000 is the clock used at the World Championship, the Candidates and the World Cup.

For club chess you do not need one. Most clubs, ours included, provide clocks on the night — and several perfectly good alternatives (Leap, Chronos, ZMF) are covered in our guides alongside the DGTs.

One last habit worth building

Press the clock, then write your move down — not the other way round. Every second spent with a pen in your hand is a second off your own time, and in a tight endgame that is where games get lost.

New to over-the-board chess? Our guide to learning chess covers getting started, and if you are near west Kent you would be very welcome at the club — we play every Monday evening, clocks provided.