French grain directions are indicated by the dimensional order of the sheet size. For example, 25x38 would indicated the grain is long in the 38" direction. If the size is listed as 38x25, the grain will be long in the 25" direction.

GRAIN DIRECTION: Direction of predominant fiber alignment, usually the machine direction. The directionality of paper must be taken into account in measuring such paper strength properties as tear, tensile, and folding endurance. Grain direction can also influence the curl of a cut sheet if it is stretched or moistened.