What's the Difference Between Increment and Delay in Chess Clocks?

In the early days of competitive chess, timers were simple countdown clocks. Once your time ran out, you lost—a mechanic known as "sudden death." This often led to chaotic time-scrambles where players focused on knocking over pieces and slamming buttons as fast as possible, rather than finding quality moves.

To solve this, modern digital clocks introduced extra time extensions: increments and delays.

While they both aim to give players a buffer to complete their games strategically, they function in very different ways. In this article, we will explain the mechanics of Fischer Increment, US Delay, and Bronstein Delay, and how they affect your gameplay.

1. Fischer Increment (The Standard)

Invented and patented by former World Champion Bobby Fischer, the Fischer Increment is the most popular time control system in modern chess and is the official standard for FIDE tournaments.

How it works:

A fixed amount of time (e.g., 3 seconds) is added to your clock before every move.

•If you have 10 seconds left, and the increment is 3 seconds, your clock immediately goes up to 13 seconds when your turn starts.

•If you make your move in 1 second, you keep the remaining 2 seconds. Over many moves, your total remaining time can actually increase beyond your starting time if you play faster than the increment rate.

Best for: Encouraging accurate, strategic endgames. Because time accumulates, you can build up a healthy time buffer by making quick, forced moves.

2. US Delay (Simple Delay)

Commonly used in tournaments sanctioned by the United States Chess Federation (USCF), US Delay does not add any time to your clock. Instead, it pauses the countdown.

How it works:

When it becomes your turn, the clock waits for the delay duration (e.g., 5 seconds) before it begins subtracting time from your main pool.

•During this delay window, the clock displays a countdown of the delay seconds.

•If you make your move within the 5-second delay period, your main clock remains unchanged.

•If you take 8 seconds to move, only 3 seconds are deducted from your main time.

Unlike increments, your total time can never increase beyond what you started your turn with.

Best for: Preventing time losses in completely won positions, without allowing players to hoard extra time.

3. Bronstein Delay

Named after Grandmaster David Bronstein, this method is a hybrid of increments and delays. It accomplishes the same mathematical result as US Delay but displays the time updates differently.

How it works:

Instead of waiting before the countdown starts, the clock ticks down immediately. However, once you complete your move and press the button, the time you used (up to the delay limit) is added back to your clock.

•If the delay is 5 seconds, and you take 3 seconds to move, 3 seconds are added back when you hit the button.

•If you take 10 seconds, only 5 seconds (the maximum delay) are added back.

•Just like US Delay, your clock can never exceed the time you had at the beginning of the turn.

Best for: Players who prefer to see their clock tick down in real-time but still want the exact mathematical safety net of a delay.

Summary Comparison Table

How to Test Them Yourself

If you want to feel the difference between these timing modes first-hand, download a customizable digital chess timer app like Knight Clock. It lets you toggle and configure all three modes instantly on your Android device, helping you choose the format that fits your playstyle.