A process for realizing blanks for the manufacture of boxes to measure, characterized in that it includes the following stages: —collecting at least a sheet of packing material from at least a store; —transferring it to a cutting station in which the sheet itself is cut so that a plurality of pieces is obtained therefrom, which plurality of pieces exhibits a common dimension and other dimensions which are different from one another according to predetermined ratios; —collecting the pieces, according to the dimensions of the box to be formed, in order to cut them into the predetermined dimensions, after joining, when necessary, one or more of said dimensionally homogeneous pieces so as to form a piece that is longer than the one available and suitable for constituting the “bottom” piece, which includes the bottom and at least two first opposite lateral walls of the box to be formed; cutting to measure said pieces and subjecting them singly to a first and a second marking in order to obtain weakened or folding lines in predetermined positions; —and after removal, if necessary, of corner portions of some pieces, carrying out the composition thereof in order to form a single body constituting the blank, flat, complete and ready to be folded and glued to form the box.