50-move rule - Chess glossary term
50-move rule
Definition
The 50-move rule is a drawing rule in chess that allows either player to claim a draw if, during the last 50 moves by each side (i.e., 100 consecutive half-moves or plies), no pawn has been moved and no capture has been made. The counter resets to zero immediately after any pawn move or capture.
Important nuance: “move” here means a full turn by both players, not a single half-move. So the rule is satisfied after 50 full moves by each side without a pawn move or capture.
How it is used in practice
Over-the-board (FIDE) play distinguishes between a claimable 50-move draw and an automatic 75-move draw:
- Claimable 50-move draw: A player having the move may claim a draw if the last 50 moves by each side have been made without any pawn move or capture. A player may also write down a legal move that, if played, would complete the 50-move sequence and claim the draw before executing the move. The correct procedure is to stop the clock and call the arbiter.
- Automatic 75-move draw: If 75 moves by each side occur without a pawn move or capture, the game is drawn automatically by the Laws of Chess (checkmate, if it occurs on the 75th move, overrides this).
Online platforms typically either enforce the 50-move draw automatically or provide a claim button; details vary by site and time control.
Strategic significance
- Attacking side: When tablebases or endgame theory assert a theoretical win that may take longer than 50 moves without a capture or pawn move, the attacker often tries to force a reset of the count by engineering a capture or a purposeful pawn advance at the right moment. Timing these resets is a key practical skill.
- Defending side: The defender aims to avoid pawn moves and avoid being forced to allow a capture, steering toward “fortress” positions and precise setups (e.g., in rook-and-bishop vs rook defenses) that resist progress until the 50-move count expires.
- Endgame tablebases: Modern 7-man tablebases show some positions are won with perfect play but require far more than 50 moves to convert without a pawn move or capture. Practically, these positions are drawn under the 50-move rule unless the winning side can force a reset.
Historical notes
A version of the 50-move rule has existed for centuries to prevent interminable games. In the 20th century, FIDE at times allowed specific exceptions (extending the limit for certain notoriously long endgames), but these exceptions were removed, returning to a universal 50-move standard for claims. In the 2010s, FIDE supplemented the claimable 50-move draw with an automatic 75-move draw and an automatic 5-fold repetition rule, strengthening the mechanisms that end games that cannot make further tangible progress.
Examples
- Counting example: Suppose the last pawn move or capture occurred on move 60 (e.g., 60...cxd4). If no pawn moves or captures occur from moves 61–110, then after Black’s 110th move the position is eligible for a 50-move draw claim by either side. If at any point a pawn advances or a capture occurs, the count resets to zero from that move.
- Rook and bishop vs rook: This endgame is often theoretically drawn but contains positions that are winning with perfect play in more than 50 moves without a capture or pawn move. In practical chess, the defender can frequently hold by avoiding any resets and aiming to “run out the 50.” Conversely, the attacker tries to force a concession (a capture or a pawn push) to restart the count and keep pressing.
- Longest-game anecdote: The marathon game Nikolić vs. Arsović, Belgrade 1989, lasted 269 moves. Although the game featured various material changes (which reset the counter along the way), it illustrates how the 50-move rule interacts with ultra-long endgames: without captures or pawn moves, the defender can use the rule to secure a draw.
Procedural details and tips
- How to claim (OTB): If you believe 50 moves by each side have passed without a pawn move or capture, write down your intended move (if needed to complete the sequence), stop the clock, and summon the arbiter to verify and declare the draw.
- What resets the count: Only pawn moves and captures. Checks, promotions that come from a pawn move (which also reset), or king/rook moves do not affect the counter by themselves.
- Interaction with other draw rules: The 50-move rule is separate from repetition. You can claim a draw either via threefold repetition or via the 50-move rule if the respective conditions are met; fivefold repetition and the 75-move rule are automatic draws.
Interesting facts
- Tablebases sometimes show “wins” that require hundreds of moves without a pawn move or capture. Such wins are unenforceable under the 50-move rule unless the attacker can compel a reset, which is why practical and tablebase evaluations can differ.
- Endgame literature and engine tablebases include special metrics like DTZ50 (distance-to-zero, with the 50-move rule in mind) that tell you how many moves until the next capture or pawn move is required to preserve a theoretical win.