What is increment in chess?

Increment is a fixed number of seconds added to your own clock every time you complete a move and press. In a 3+2 game you start with three minutes and get two seconds back after every move you make. Ask what is increment in chess and this is the part that matters: because the seconds are added rather than merely protected, your clock can go up. Move quickly enough and you can finish the game with more time than you started with.

The notation is base+increment. 3+2 means three minutes plus two seconds a move. 15+10 means fifteen minutes plus ten seconds. 90+30 means ninety minutes plus thirty seconds, a common classical control. You will also see increment called Fischer increment, bonus time, or cumulative mode. They are all one mechanism.

Why Bobby Fischer proposed it

Fischer filed a patent for a digital chess clock on 5 August 1988. It was granted on 28 November 1989 as US 4,884,255, “Digital chess clock”, inventor Robert J. Fischer. The patent's own reasoning is that adding a preset amount of time after every move guarantees a player a minimum amount of time for the next move, which reduces time scrambles. Under a plain time limit, a player who reaches a winning position with seconds left has to bang out the rest at whatever speed the clock allows, and the result stops depending on the chess. A few seconds a move removes that without giving anybody unlimited thinking time.

The clock had its public showing in the 1992 Fischer–Spassky rematch, which was played with it. Increment is now standard in FIDE classical and rapid events and in most serious online play, though it is not universal: simple delay remains common in United States tournaments, and a great deal of online blitz and bullet is still played with no increment at all.

What is increment in chess: the arithmetic

Your break-even point is the increment itself. Spend less than the increment on a move and your clock rises; spend more and it falls. In a 3+2 game a player who averages one second a move gains one second a move, so forty moves leave that player forty seconds richer than at the start.

Here is the calculation in full. Time left equals starting time, plus the increment multiplied by the number of moves you have completed, minus the thinking time you actually spent. The column below labelled “seconds used per move” is thinking time only, before the increment is credited.

Row two is the one to remember. Two seconds a move in a 3+2 game is exactly break-even, so after forty moves the clock reads 3:00 again. Row six shows the same effect at classical speed: two and a half minutes a move for forty moves is 100 minutes of thinking, more than the 90 minutes you were given, and the 30-second increment is what leaves you with ten minutes on the display instead of a flag.

If the numbers behind a specific control are what you are after, the breakdown of 3+2 works through one game move by move.

Is the increment credited before or after your first move?

Clocks differ, and both behaviours are defensible. FIDE's glossary describes increment as an amount of time added from the start before each move, which reads as though the seconds for move one are already yours; some tournament clocks are set up that way, so a 5+3 game shows 5:03 before White touches a piece. Many others, including most online clocks, start at 5:00 and add the three seconds when you press. The totals match either way: after n completed moves you have received n increments. The only difference is whether the seconds for move one are available while you play move one.

What increment does to endgames

This is where increment changes the game rather than just the clock. A 30-second increment means you can always play on: half a minute is enough time to find each move when you are walking a lone king to the edge with a rook, or converting an extra queen, so a won position tends to stay won instead of being decided by hand speed.

The rules reflect that. FIDE keeps a draw-claim procedure for quickplay finishes, where a player with under two minutes left can ask an arbiter to declare the game drawn on the grounds that the opponent cannot win by normal means, or has made no effort to do so. That procedure covers standard and rapid games played without increment, and only where the competition rules provide for it. Put an increment on the clock and the argument does not arise.

Losing on time is also not automatic. If your flag falls in a position where your opponent could not checkmate you by any possible series of legal moves — a bare king, for instance — the game is a draw rather than a loss. Note that this is about whether mate is possible at all, not whether it can be forced.

Small increments behave differently. Two or three seconds a move keeps a blitz game moving, but a long technical win still costs more time than it pays back, so you have to be fast as well as right. Around ten seconds a move, most club players can play out a basic endgame without the clock deciding it.

Typical increments by category

FIDE classifies a game by base time plus sixty times the increment. Ten minutes or less by that formula is blitz; more than ten and under sixty minutes is rapid; sixty minutes or more is standard, or classical. So 3+2 counts as five minutes and is blitz, 5+5 lands exactly on the ten-minute boundary and is still blitz, and 15+10 counts as 25 minutes of rapid. Online sites label things more loosely, which is why a 10+0 game that FIDE would call blitz sits under rapid on most websites.

Bullet is a site label rather than a FIDE category, and the boundaries move: 2+1 is bullet on some sites and blitz on others. Staged controls are the other complication. The 2024 world championship match used 120 minutes for the first 40 moves, then 30 minutes for the rest, with a 30-second increment from move 41 — increment can be switched on partway through a game rather than from move one. Controls of that kind are covered in the guide to chess time controls.

Increment is not delay

Delay protects time; increment adds it. With a three-second simple delay your clock pauses for three seconds at the start of every move and only then starts counting down, so the best you can do over a three-minute game is finish on 3:00. With a three-second increment you can climb above your starting time. Bronstein delay is the other bookkeeping: your clock runs immediately and you get back whatever you used, up to three seconds, which leaves the same time remaining after each completed move as simple delay does, even though the display behaves differently while you think. The side-by-side comparison shows what each one does to the same position.

Set an increment and play

The increment chess clock on this site runs in your browser with no account and no install: pick 3+2, 5+5 or 15+10 from the presets, or build your own base and increment from one to sixty seconds. The same clock engine elsewhere on the site also runs simple delay, Bronstein and multi-stage tournament controls, so you can compare the modes on one position.

For over-the-board games away from a laptop, the Chess Timer app runs Fischer increment offline on your phone, with presets from 1 minute up to 30 minutes and manual +10s / −10s arbiter corrections. It is increment only — no delay or Bronstein mode, and multi-stage controls can be saved but are played as their base time plus increment. The app is a free download on the App Store and Google Play, with a premium unlock after the first few start and pause actions.