Depth to Conversion

Depth to Conversion, abbreviated DTC, is a tablebase metric. A tablebase is a precomputed collection that knows the correct result of every covered position for specified combinations of endgame pieces.

Conversion here means changing the set of pieces present on the board. It normally occurs through a capture or a pawn promotion, when a pawn reaches the last rank and becomes another piece. Mate also ends the measurement if it comes first. An ordinary pawn push that does not promote is not by itself a DTC conversion.

In a won position, the winning side chooses moves that preserve the win and reach conversion as soon as possible, while the defender tries to delay it. The value does not necessarily describe the shortest mate. A line may convert quickly into another won ending and still require many moves before checkmate.

DTC is also different from distance to zero, which concerns the next move that resets the counter relevant to the fifty-move rule. Units and sign conventions can differ among formats, so an interface should state how it presents the number.