For everyone at the board · 8 min read
How does a chess clock work? Time controls explained
What 15+10 means, why you press with the same hand, what happens when the flag falls, and which time control suits a club night.
By Castle Gambit · Updated
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The short answer
A chess clock is two timers joined together: after you move, you press your button, which stops your time and starts your opponent’s, and whoever runs out of time first loses (unless the other player couldn’t possibly checkmate). A time control like 15+10 means each player starts with 15 minutes and gains 10 seconds after every move.
Key takeaways
- Move first, then press the clock, with the same hand you moved with.
- 15+10 means 15 minutes each, plus 10 seconds added after every move you make.
- Under FIDE rules, blitz is 10 minutes or less each, rapid is more than 10 and under 60, and 60 or more is standard (classical).
- FIDE counts an increment as if the game lasted 60 moves: 10+5 works out to 15 minutes, so it’s rapid, not blitz.
- For a casual club night, 10+5 or 15+10 is a good default: games finish, and nobody loses a won position in a scramble.
The first time someone slides a chess clock onto your table, it can feel like the game just got a lot more serious. It hasn’t, really. A clock is just a fair way of sharing time, and after two games you’ll press it without thinking. Here’s how it works, what the numbers mean, and what to set it to on a club night.
What a chess clock does
A chess clock is two timers joined together, one for each player, built so that only one can run at a time. While it’s your move, your time runs down. When you’ve moved, you press your button: your clock stops and your opponent’s starts.
Each player gets a budget of time for the whole game, not for each move. Spend it however you like: race through the opening, then think for ten minutes about one tricky position. Managing that budget is part of the game, and it’s the reason a club night can fit three or four games into an evening instead of one very long one.
Old analog clocks have a little red flag that the minute hand lifts as it nears the hour, and that drops when time runs out. That’s where “the flag fell” comes from. Digital clocks show a flag symbol or simply 0:00.
How to use one
Set it before you start, and check both sides show the same time.
Put it to one side of the board, where you can both reach it and see it. At a tournament, the arbiter decides.
Start White’s clock. By custom, the player with Black presses to start White’s clock, and the game is on.
Move, then press, with the same hand you moved with. Under FIDE rules that’s required, and it keeps the game fair.
Don’t hover, don’t punch. Take your hand away from the clock between moves, and press it; don’t slam it.
Need to stop the game, to fix a knocked-over piece or to ask the organizer something? Pause the clock (most digital clocks have a button for it), sort it out, and start it again. At a tournament, stopping the clocks to call the arbiter is always allowed.
When the flag falls
If your time runs out before the game is over, you lose on time. It doesn’t matter how good your position is: the clock is part of the game.
There’s one important exception. Under FIDE rules (Article 6.9), if your time runs out but your opponent couldn’t possibly checkmate you by any series of legal moves (say, they only have a king and a knight left), the game is a draw instead.
Reading a time control: 15+10, G/30, d5
A time control is the clock’s settings, written as a little formula. The most common kind you’ll see at a club is 15+10: fifteen minutes each, plus ten seconds added after every move you make.
| Written | What it means |
|---|---|
| 15+10 | 15 minutes each, plus 10 seconds added after every move |
| 10+5 | 10 minutes each, plus 5 seconds a move |
| 5+0 | 5 minutes each, nothing added: when it’s gone, it’s gone (“sudden death”) |
| G/30 | US Chess style: game in 30 minutes each, sudden death |
| G/30;d5 | Game in 30 minutes, with a 5-second delay before your clock starts counting each move |
| 90/40, 30, +30 | 90 minutes for the first 40 moves, then 30 minutes for the rest, plus 30 seconds a move throughout (a classic FIDE standard control) |
The number before the plus is minutes; the number after it is seconds. Mix them up once and you’ll never do it again.
Increment vs delay
Both increments and delays solve the same problem: without them, a player can lose a completely won position just because they can’t physically move the pieces fast enough in the last few seconds. They just do it in slightly different ways.
- Increment (also called Fischer, after Bobby Fischer, who proposed it): after each move, a few seconds are added to your clock. Move quickly and you can build up time.
- Delay (simple or US delay): each time your clock starts, it waits a few seconds before it begins counting down. Move within the delay and it costs you nothing, but you can never bank extra time.
- Bronstein delay: after your move, the clock gives you back the time you just used, up to a limit. Like an increment you can’t save up.
FIDE events use increments. Many US tournaments use delay. At a club night, use whatever your clocks make easy; increments are the most common.
Blitz, rapid and classical
FIDE sorts games into three speeds by how much time each player has. To compare controls with and without an increment, it counts the increment as if the game lasted 60 moves: 10 seconds a move for 60 moves is 10 minutes, so 15+10 counts as 15 + 10 = 25 minutes each.
- Blitz: 10 minutes or less for each player.
- Rapid: more than 10 minutes and less than 60.
- Standard (classical): 60 minutes or more.
Faster than blitz is “bullet” (a minute or two each), which lives mostly online. US Chess draws its lines a little differently, so a US tournament’s own flyer is the place to check.
Which time control for a club night?
For a casual club night, you want games that finish, a pace newcomers can enjoy, and enough time that the end of the game is still chess rather than a slapping contest. Some good defaults:
| Control | A game lasts up to about | Good for |
|---|---|---|
| 15+10 | 50 minutes | The friendly default: thinking time, and no scrambles |
| 10+5 | 30 minutes | More games in an evening; still rapid, not blitz |
| 5+3 | 16 minutes | The last half hour, when the room gets lively |
| No clock | As long as it takes | Beginners, kids’ clubs, and teaching games |
Those lengths assume both players use all their time over a 60-move game, so they’re the long end: most games finish well inside them. A very long endgame with an increment can run a little over.
Organizing the night? How to run a chess club night has the rest of the evening.
Setting up a clock, and buying one
Every digital clock is set a little differently, but they all ask the same questions. Many have their preset programs printed on a card inside the lid or in the manual; the common ones are usually a button or two away.
Pick the mode: sudden death, increment (often labelled Fischer), or delay (US delay or Bronstein).
Set the time for each player: the same on both sides, unless you’re playing time odds.
Set the increment or delay, if there is one.
Check both displays before the first move. Then check the batteries once a month, because clocks die at the worst moment.
If you’re buying clocks for a club, look for:
- Increment and delay both, which nearly every digital clock has now.
- A clear display you can read from across a board, with an obvious sign of whose clock is running.
- A pause button.
- Sturdy buttons, because they will be pressed ten thousand times, some of them hard.
Analog clocks are beautiful and can’t do increments. Keep one on the shelf for atmosphere, and use digital ones for play.
