Guide · Updated September 2026

How to use a chess clock: the rules and etiquette that matter

Most arguments over a chess clock are not about the time. They are about which side it sits on, which hand hit it, and who noticed the flag first. Here is what the major rulebooks expect, plus the courtesy that keeps a club night friendly.

Need a clock on the table? TockRelay is free on the App Store and Google Play.

What should you check before the first move?

Most clock trouble starts before the game does. Take thirty seconds to confirm three things with your opponent:

• The time control. Base time, plus whether there is an increment or a delay and how many seconds. "Game in 30" with a 5-second delay and 30 minutes with a 5-second increment are not the same game — see increment vs delay.
• The starting times. Both sides should show the same starting time unless you have deliberately agreed to time odds.
• The clock itself. If an event supplies equipment, you use it. A US Chess rules column notes that when players bring their own clocks, the preferred clock is the one that can be set for the announced time control.

Which side of the board does the clock go on?

This depends on whose rules you are playing under. The FIDE Laws of Chess say that before the game starts, the arbiter decides where the clock is placed. In US Chess play, the player with the Black pieces generally chooses which side of the board the clock goes on. The common exception, noted in ChessKid's guide, is when the organizer has already placed clocks at every board facing the same direction — then you leave them as they are.

At a casual game the courtesy version is simple: put the clock where both players can reach it without stretching across the board, and if one player is left-handed, ask.

How do you press the clock correctly?

Three habits cover almost every dispute:

1. Finish the move first. Put the piece down on its square, then press. Pressing is how you tell the clock your move is complete.
2. Use the same hand you moved with. The FIDE Laws require a player to press the clock with the same hand used to make the move, and ChessKid's guide gives the same rule for scholastic players. Moving with one hand while the other waits on the clock is exactly what the rule prevents.
3. Don't hover, hold, or slam. FIDE forbids keeping a finger on the clock or hovering over it. Slamming is a problem too: ChessKid notes that it breaks US Chess rules against disturbing noises. A firm, ordinary press is all a clock needs.

Also press your own side. Touching your opponent's side, or adjusting their clock, is a quick way to start an argument you will not win.

What happens when a flag falls?

On an analog clock the flag is a small lever that drops when time runs out; digital clocks mark the same moment on screen. When your flag falls, you normally lose on time. Two details matter:

• Who can call it. Under the FIDE Laws, a flag is considered to have fallen when the arbiter observes it or when either player makes a valid claim. ChessKid's guide for young tournament players puts it plainly: noticing your opponent's flag is your job, and you should not point out a fallen flag on someone else's board.
• The checkmate exception. Under the FIDE Laws, if your time runs out but your opponent could not checkmate your king by any possible series of legal moves, the game is drawn rather than lost. A lone king cannot win on time.

In a friendly game, agree before you start whether you will play on after a flag or stop. It saves an awkward conversation at 0:00.

When are you allowed to stop the clock?

Rarely. The FIDE Laws allow a player to pause the clock only to seek the arbiter's assistance — for example, when a pawn promotes and the piece you need is not on the table. ChessKid's guide gives the scholastic version: pause only to call a tournament director, not to visit the restroom, record moves, or argue with your opponent. If you are unsure whether something needs a ruling, stopping the clock and asking is better than guessing.

Step by step: running the clock in one game

1. Agree on and set the time control, including any increment or delay, and check both starting times.
2. Place the clock — by the arbiter's decision under FIDE rules, or usually by Black's choice under US Chess rules unless the organizer has pre-positioned clocks.
3. Start White's clock. White moves first, so White's time runs first.
4. Move, then press with the same hand. No hovering, no holding, no slamming.
5. Watch for a fallen flag, and remember that a game is drawn rather than lost on time when the opponent could not possibly checkmate.
6. Stop the clock only for the arbiter or tournament director.

Can you use a phone as a chess clock at a tournament?

Not without permission. The FIDE Laws forbid a player, during a game, from having any electronic device in the playing venue that the arbiter has not specifically approved. Organizers of other events set their own policies on phones in the playing area. A phone clock app — TockRelay included — is not certified tournament equipment, and should not be used in a rated event unless the organizer has approved it.

Where a phone clock shines is everywhere else: club nights, school chess clubs, kitchen tables, park benches, coaching sessions, and practice for an event's exact time control.

Etiquette that isn't in the rulebook

• Silence your clock sounds in a shared room unless everyone wants them.
• Lay a phone clock flat and centered beside the board so neither player has to reach across the pieces.
• Leave your opponent's clock alone, including comments about it. Their time is their business until it runs out.
• Agree on the result before resetting the clock, so the final times are still there if anyone asks.

For how the time controls themselves are categorized, see chess time controls explained.