How to Use a Chess Clock
Analog and Digital Chess Clocks

How to Use a Chess Clock

by Steve Lopez

Beginning chess players, and those unfamiliar with chess playing software, are often unsure of the reasons why a chess clock is used or how to operate one. Even experienced players who've never played at a chess club or in a tournament become confused when these topics come up.

The reason why chess clocks are used is to ensure that each player has a limited, finite amount of time in which to complete a game. While this might seem obvious or even humorous to us today, the time issue was a real problem back in the mid-1800's. It was not unusual for a player to take literally hours to make a single move. Games between professional players sometimes took days to complete, and a match (a series of games) between a pair of players could consume weeks or even months. If a game or match was contested between a younger and much older player, there sometimes occurred a form of unfair "gamesmanship" on the part of the younger player in which he'd try to wear down the older player by taking so long with his moves that the older player would become fatigued, even ill.

The chess clock solved this problem. The clock regulates the time consumed by each player individually; the players start with the same amount of time in which to make their moves, and a player loses the game when his time runs out (regardless of the position on the board).

There are two kinds of chess clocks: analog and digital. A traditional analog clock looks like this:

Analog Clock -Timekeeper

Since the late 1990's, the digital chess clock has become increasingly prevalent at chess tournaments, primarily because these allow some unusual time settings (which we'll discuss later) that are impossible to use with analog clocks. The typical digital display looks like this:

Digital Chess Clock and Game Timer

Although digital clocks are more versatile than analog models, the traditional analog clock shows no signs of going away soon and still seems to be the favorite at chess clubs (at least at the gatherings I attend), mainly due to their ease of use. While digital models produced by different manufacturers often have specific directions for setting them, instructions which differ from model to model, analog clocks have a standard stem which the user turns to set the time - thus all analog cloks work essentially the same way, and if you can set one, you can set them all.

How a Chess Clock Works

Before we begin discussing the various time controls used in chess, we should first look at how a chess clock works. A "chess clock" is actually two connected timepieces, constructed so that only one clock may run at a time. An analog clock has two large buttons on its upper surface; when one of these buttons is pressed, the other clock starts running. So, to begin a game of chess, the player of the Black pieces (right) presses his clock's button to start the White player's clock: 


In the above illustration, Black's button (on the right) has been pressed. This pops White's button up and White's clock is now running. Many analog clocks have oversized buttons and stems, and the stems are often brightly colored (usually white or red); this makes it easy to tell from a distance whose clock is running, which is useful at large chess tournaments when players often go for a walk to stretch their legs while their opponent is thinking. 

Now White has made his move and pressed his button to start Black's right side clock; it will continue to run until Black has made a move. After Black moves, he'll press the button on his own clock - this will stop Black's clock and start the White player's clock.
Thus each player has a clock which runs only when it's his or her turn to move and it therefore keeps track of that player's "thinking time". This back and forth process of hitting a button after each move to stop one's own clock and start the opponent's clock repeats until the game ends through checkmate, draw, or one player running out of time.

An analog chess clock has a flag mounted at about the number "11" on the clock's face (not shown in these illustrations). The clock's minute hand begins pushing the flag upward as it passes the "11"; when the hand reaches the number "12" the flag drops. It's traditional in United States chess events to set a chess clock so that the "final flag" falls when the clock displays six o'clock (instead of midnight as shown in the above illustrations). We'll discuss this a bit later.

Digital chess clocks show a "countdown display" telling each player how much time they have left:

This works just like "bomb clocks" you've seen in adventure movies: a clock runs backwards until reaching "zero", at which point that player loses the game. Digital clocks may not even have large protruding buttons as analog clocks do, but instead a flat pressure-sensitive pad which acts as a button to stop one's own clock and start the opponent's. They definitely don't have a "flag", although many digital clocks can be set to make a beeping sound (or some other audio cue) at intervals when a player's time has reached five minutes or less (this use of such audio signals, however, is sometimes discouraged in chess tournaments as the sound may disturb other players at nearby boards and may even technically be illegal according to some chess federations' rules).

Each style of clock has its advantages and disadvantages. Analog clocks are easier to read from a distance and their light-colored stems make it easy to see whose move it is (even from across a room); also, since the procedure for setting them is nearly universal, nearly anyone can set an analog clock without special instructions. Analog models tend to be a bit less accurate, however, than digital clocks, and a (unfortunately too common) ploy late in a game is to roughly handle a clock to try to make the opponent's flag fall prematurely. Digital clocks, although much more difficult to read at a distance, are more accurate than analog clocks and rough handling of them won't cause a player to unfairly lose time. Digital clocks are also capable of being set for "incremental" time controls, an impossibility for traditional analog clocks.

The time controls used in chess fall into two broad categories: traditional time controls and incremental (often called "Fischer") time controls. (There are a few additional and seldom-used time controls, such as "rapid transit", which aren't recognized for official tournament use. We'll discuss them very briefly at the end of this article.)

Traditional Time Controls in a Chess Clock

Traditional time controls were the order of the day, the "official" means for timing a chess game, for more than one hundred years and are still quite frequently used today. Understanding them is the key to understanding the slightly more complex incremental time controls which we'll look at a bit later.

The easiest time control to understand is called "sudden death", in which each player has x amount of time to complete all the moves of the game. No matter how many moves a game lasts, when a player runs out of time he loses the game (regardless of whether he's "winning" materially or positionally on the chessboard). For example, "Game in 30" means that each player has thirty minutes on his clock at the start of the game. This is how a "Game in 30" time control would appear on an analog clock:

The clocks are set to "11:30"; if a player's clock reaches "12:00" he runs out of time (having used more than the allotted thirty minutes) and he loses. (As stated previously, it's traditional in U.S. events to set a clock so that a player loses when it reaches "6:00", so in this case the clocks would be set to "5:30").

On a digital clock, the start of a "Game in 30" contest would look like this:

It's easy to know the maximum amount of time a sudden death game could last: simply multiply the time control by "2". In the case of a "Game in 30" contest, a game can't possibly last longer than an hour since each player has a maximum of thirty minutes for all of his moves. That's why sudden death tournaments are so easily set up by organizers: since organizers know the maximum length for each game, they can easily schedule a time for each tournament round to start. For example, if the time control is "Game in 60", the rounds should be scheduled to start no closer than two hours from each other (since two hours is the maximum time a game can last).

In advertisements for chess tournaments, these sudden death time controls are usually designated with a "G" followed by a slash and the allotted time in minutes. Thus a "Game in 60" event would be written as "G/60", a tournament in which each player has thirty minutes a game would appear as "G/30", and a blitz (five minute) tournament would be "G/5". You'll also sometimes see this information provided in the game headers for chess games published in magazines or on the Internet.

The traditional, more "open-ended" time control which was used for many years was "forty moves in two hours" (often written shorthand as "40/2"). A clock would be set so that each player had two hours showing:

Each player had to make his fortieth (40th) move by the time two hours were up; if his flag fell before his fortieth move was made, he lost.

But what happens in games which last longer than forty moves? This is why such games always have a secondary time control. For example, a professional chess tournament might be listed as "40/2, 20/1". This means that the players are required to make forty moves within two hours on their clock, and have to make twenty moves each hour thereafter. When they make their fortieth move, any time remaining on their clock is added to the time specified by the secondary time control, and this is the amount of time he's allotted in which he must make it to move 60.

Let's look at a practical example. In a "40/2, 20/1" event, White makes his 40th move and has exactly 15 minutes remaining on his clock. That 15 minutes is added to the 60 minutes of the next time increment. He now has 75 minutes (an hour and fifteen minutes) to make it to move 60. Let's say that the analog clocks are set to ten o'clock at the game's start (as in the illustration above); the clocks don't need to be reset when the player makes it to move 40 - now he has until his clock reads one o'clock to make to to move 60 (since the secondary time control was 60 minutes, or exactly one hour, you just add the one hour to his remaining time and play to the clock reading one o'clock instead of to twelve o'clock).

Once each player has made it to move 60 in such a tournament or match, you'd add another hour to their remaining time and they have to make it to move 80 before this new allotment runs out.

It probably sounds more complicated than it is; the concept is really amazingly simple once you've grasped it. But there's still a fly in the ointment with this traditional "open ended" time control: there's no way to know how long a game can possibly last - there's no set "maximum" game length.

This is why tournament organizers (at least at the amateur level) often use a mix of traditional and sudden death time controls. For example, I used to play in a lot of three day chess events back in the early 1990's. The usual time control for such six game tournaments was "40/2, G/1", which translates as "forty moves in two hours, followed by sudden death in one hour". Setting our analog chess clocks to four o'clock, we had until our clocks read six o'clock to make forty moves. Once you'd made your 40th move, you then added one hour (the "sudden death" time control) to your remaining time and had until your clock read seven o'clock to finish your game (no matter how many moves the game lasted). Thus each player had a maximum of three hours to make all of his moves; a game could last six hours at most, and thus the tournaments's rounds could be scheduled six hours apart.

Incremental Time Controls Using a Chess Clock

In 1992, former world chess champion Robert J. "Bobby" Fischer returned from a self-imposed exile to play a match against his old foe Boris Spassky. Fischer used the occasion of his return (and the world-wide media blitz) to promote a new chess time control he claimed to have developed himself. In reality this "new" time control had been used for years by players of the Japanese strategy game go-moku (or "Go"), but Fischer is correct in that he was the first to seriously promote it as a means of timing chess games. It's thus often referred to as the "Fischer time control".

The traditional time controls we've already discussed contained, in Fischer's opinion, serious flaws. The use of sudden death time controls meant that the endgame was usually rushed by one or both players and that games were often decided by fatal errors rather than by great play. Open-ended time controls were a problem for tournament organizers who had to arrange for the use of a facility to host a tournament or match; if there was no way to know how long the games of an event would last, there was no way to arange in advance for the use of a building or facility to house the event.

Fischer's solution was a sort of "middle ground approach". In the time control which he advocated (again, already used by professional Go players for quite a while) a small amount of time (an "increment") was added to a player's remaining time after he made a move. These increments were usually much shorter than the average time the typical player takes in deciding on his move, so that a player would still usually lose time whenever it was his turn to move (and thus a game couldn't/wouldn't last forever). But, in theory, if a player could move fast enough each time it was his turn, he need never worry about running out of time and losing a game "by the clock". It was also theoretically possible to use an algebraic formula to approximate the maximum time a game could last, thus allowing event organizers to arrange for the use of a facility to house the event. The downside of this incremental time control was to make analog clocks effectively obsolete; a digital timer would be required to properly time incremental games.

You'll notice the repeated use of the world "theory". Let's see how the Fischer" (incremental) time control works in practice.

You start with a predetermined "sudden death" time control - let's say forty minutes. The "increment" used will be twenty seconds, which means that when a player makes his move and hits the button on his clock, twenty seconds will be added back to his time allotment. In theory (there's that word again), as long as a player always makes a move in under twenty seconds, he'll actually gain time on his clock. (By the way, this time control we're discussing would be written as "40/20", meaning that the game will have a forty minute initial time allotment with twenty seconds added on after a player makes a move.)

Let's look at an example of a player's time usage (and his corresponding clock display) across the first few moves of a 40/20 Fischer increment game.

The White player at the start of such a game has "40:00" showing on his digital clock, which means that he starts with forty minutes in which to make all his moves. Black hits his button to start White's clock (and to start the game). White already knows what he wants to play, makes the move 1.e4, and hits his clock to complete his move. Three seconds have elapsed between the time Black hit his clock to begin White's move and White hitting his clock to end the move.

In a traditional "sudden death" game, White's clock would read "39:57" (showing that three seconds had been used) and that would be it. But since this is a "Fischer" time control game with a twenty second increment, the digital clock has been pre-programmed to add twenty seconds back to a player's time whenever his button is pushed. Thus twenty seconds gets added to White's clock when he presses the button to finish his move, and the timer's display now reads "40:17" (his initial 40 minutes - the 3 seconds he took to move + the 20 "bonus" seconds of the added increment):

40:00 - 0:03 = 39:57
39:57 + 0:20 = 40:17

Black plays 1...e5 and hits his clock to end his move and start White's timer. The White player snaps off 2.Nf3, again taking three seconds to make his move and hit the button on his timer:

40:17 - 0:03 = 40:14
40:14 + 0:20 = 40:34

...and so White has actually gained 34 seconds since the game's start because he's playing pretty quickly.

Black bangs out 2...Nc6 and hits his clock. The White player already knows he wants to play a Ruy Lopez and plays 3.Bb5, again taking three seconds to make his move and hit his clock:

40:34 - 0:03 = 40:31
40:31 + 0:20 = 40:51

White's picked up nearly a full minute - he now has nearly 41 minutes to make all the rest of his moves.

But Black has other ideas; either by design or by accident, he doesn't play the standard Ruy reply of 3...a6 and instead plays 3...Nf6. This throws White for a bit of a loop as he hasn't prepared for this move. He eventually figures out a reply but takes a full two minutes and thirty-four seconds to think, make the move, and hit the button on his clock:

40:51 - 2:34 = 38:17
38:17 + 0:20 = 38:37

...and White now has 38 minutes and 37 seconds left on his clock to make all of his moves before he'd "lose on time".

I've played quite a few online games using the "40/20" Fischer increment and discovered that, on average, each player usually uses about an hour to play; this is a good increment to use when you have about two hours to play a game. For a faster game you could easily start with a shorter "sudden death" time or a shorter increment (or both, such as "20/10": twenty initial minutes with ten seconds added each move). A few algebraic equations have been published which let you approximate the time a game will take when using a particular Fischer time control; although it's impossible to predict infallibly the length of time which a (theoretically) open-ended game will take, these equations can at least give players a "ballpark" idea of the expected duration of a game.

Fischer increments were officially recognized by the United States Chess Federation for tournament use starting in the mid 1990's. This caused a fair amount of contoversy at the time since players had to replace their analog clocks with (then more expensive) digital models. That initial furor has died down over time, but you'll see many players still using their analog clocks for casual "sudden death" games at chess clubs or between rounds at chess tournaments. (In fact, an analog clock is still my choice for "speed" games with my friends and family, since anyone can understand how to set and use one without any special instructions.)

Other Time Controls Using a Chess Clock

When teaching a new chessplayer, many instructors offer "odds": that is, they'll remove some of their own pieces from the board before the start of the game, thus playing with a material handicap and providing an advantage to the less-experienced player. I've discovered that some players balk at being "given an unfair advantage". One solution is to use a chess clock to give the less experienced player a time advantage (instead of a material advantage); I've discovered that many people readily accept this form of "handicap game". When I was teaching my young (about eight years old as I recall) nephew to play, we played many, many "speed" games in which he'd have ten minutes to make all of his moves while I usually set my own clock for five minutes (or even less). This not only tended to "even things up" a bit but also allowed us to play a lot more games than we'd have played without the use of a clock, thus providing him with a lot of chess experience in a hurry.

A completely different form of time control which I often used years later when teaching my own children was "rapid transit chess", a special form in which each player has a set amount of time to make each move. Many digital timers can be set to use this variety of time control. In our case, my sons and I used specially-made one-button timers which could be set to either of two increments: ten seconds or thirty seconds.

Here's an example. When we'd use a rapid transit timer set for thirty seconds, Black would hit the button to start the game. White then had thirty seconds in which to make his first move. If he dawdled and only ten seconds were left, the timer would emit a loud "beep" once per second; if the player failed to move before thirty seconds were up, the timer would emit a long shrill beep to inform him that he'd lost the game.

If that didn't happen and a player made his move within thirty seconds, he'd hit the button on the timer. Now Black had thirty seconds to make his own move and hit the button. Once he pushed the button, White had thirty seconds to make a move, and so on until the game ended by checkmate, draw, or one player failing to move within thirty seconds of the timer's single button being pressed.

Rapid transit was a very popular form of chess back in the 1950's, especially in the famous chess clubs of New York City. It's an action-packed, adrenaline-filled way to play the game. Despite Grandmaster Yasser Seirawan's efforts to promote it in the 1990's as a means of attracting "children of the Video Game Age" to chess (and my own more recent efforts to promote it as a time control suitable for televised chess), the rapid transit time control has today become little more than a novelty and is seldom used, even in casual games; most chessplayers have never even heard of it. The overwhelming majority (in fact, nearly 100%) of club and tournament chess games use either the traditional or Fischer styles of time control.

2009, Steven A. Lopez and ChessCentral. All rights reserved. 

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