Distance to zero

Distance to zero, abbreviated DTZ, is a metric stored by a tablebase, a precomputed collection that knows the correct result of the endings it covers. DTZ measures how far a position is from mate or from a move that resets the halfmove counter to zero. The counter records how many single-side moves, called plies, have occurred since the last move that reset it.

Moves that reset the counter

• Any capture.
• Any pawn move, even when the pawn neither captures nor promotes.

The fifty-move rule permits a draw claim when each player has completed fifty consecutive moves without a capture or pawn move. DTZ does not merely seek any nearby reset: within a line that preserves the theoretical result, the winning side tries to force a zeroing move and the defender tries to delay it. The value must be interpreted with win, draw, or loss information and the current counter.

DTZ is not distance to mate. It also differs from DTC: a pawn push resets the counter even when it neither captures nor promotes, so it can be a zeroing move without being a material conversion.