About

In high-stakes chess, the clock is not just a measurement device; it is a weapon. A player must balance positional accuracy against the relentless decay of their time reserves. This tool is a tournament-grade digital implementation of a professional chess clock, designed to eliminate the latency issues common in web-based timers while offering the advanced control modes required by FIDE (International Chess Federation) and USCF standards.

Unlike basic stopwatches, this system implements the correct mathematical handling of Fischer Increment (time added per move) and Bronstein Delay (time refunded per move). It utilizes the performance.now API to calculate time deltas with microsecond precision, ensuring that the displayed time t_display exactly matches the wall-clock time t_real, preventing the "clock drift" that plagues standard JavaScript timers over long games.

Key features for serious players include Wake Lock integration (preventing screen sleep during deep thought), Arbiter Mode (allowing manual time adjustments for illegal move penalties), and visual Time Pressure indicators that shift color as the "flag" approaches.

Formulas

The precise calculation of remaining time T_rem involves accounting for the starting budget, the time consumed per move t_think, and the increment algorithm used.

1. Fischer Increment: Time is added to the reserve. The total available time after n moves is:

T_rem = T_start − n∑i=1 t_{think_i} + (n − 1) ⋅ I

Where I is the increment in seconds.

2. Bronstein Delay: The time deducted t_deduct is effectively the thinking time minus the delay D, but it can never be negative (you cannot gain time):

t_deduct = max(0, t_think − D)

If a player moves instantly (thinking time < D), the clock simply does not move, preserving the original time.

Reference Data

Preset Name	Base Time	Increment / Delay	Est. Game Duration	Tournament Context
FIDE Bullet	1 min	+ 0 sec	< 2 mins	Online "Hyperbullet" play.
FIDE Blitz	3 min	+ 2 sec	10 mins	World Blitz Championship Standard.
Club Blitz	5 min	+ 0 sec	10 mins	Casual "5-Minute" games.
Rapid (FIDE)	15 min	+ 10 sec	45 mins	World Rapid Championship.
Classical (Club)	30 min	+ 0 sec	1 hour	Weekend Swiss tournaments (G/30).
Classical (Pro)	90 min	+ 30 sec	4 hours	Top-level FIDE events.
USCF Delay	40 min	5 sec (Delay)	90 mins	US National Standard (Analog-style delay).
Armageddon	5 vs 4	0 sec	9 mins	Tie-break: Black wins on a draw.
Hourglass	1 min	Variable	Undefined	Time flows from one player to the other.

Frequently Asked Questions

Wake Lock is a browser capability that prevents your device's screen from dimming or turning off while the website is active. This is critical for chess, as games can involve long periods of contemplation without screen interaction. This tool automatically engages the Wake Lock when a game begins.

Tap the "Pause" button during a game. The overlay that appears acts as an Arbiter screen. You will see +/- buttons next to each player's time. Use these to add penalties or restore time before resuming the game.

Yes. While the presets (like 3+2) apply the same time to both players, you can manually select "Custom" setup. This unlocks independent input fields for Player 1 and Player 2, allowing you to give one player 5 minutes and the other 1 minute (e.g., for Armageddon games).

Nothing. This tool runs entirely client-side (in your browser). Once loaded, it requires no internet connection to function, making it safe for use in areas with poor signal.

Yes. We use "delta-timing" based on the system clock rather than relying on the screen refresh rate. Even if your device lags or the browser throttles the animation, the mathematical calculation of elapsed time remains precise to the millisecond.