The invention concerns a process and an apparatus for measuring the anisotropy value of form changes in normal direction in sheet metals (the r-value). In course of a standard tensile test, the longitudinal change of dimension of the test piece is measured. When a preselected value of change of dimension in longitudinal direction which is characteristic of the material of the test piece, is reacted during the measuring process, the appertaining change of dimension in lateral direction is measured. Thereafter, an r-value is selected from the r-values corresponding to different changes in dimension in lateral direction at a preselected longitudinal change of dimension, which is closest to the one measured at the change of direction in lateral direction. The apparatus comprises comparator and switching units which are connected to signal transmitters converting changes of dimension in longitudinal direction into electric signals. The comparator and switching units compare the electric input signals with reference signals. After the preselected change of dimension in longitudinal direction is reached in the course of the measuring process, these units send an interlocking signal to a further switching and decoding unit. This further switching unit is connected to a comparator unit which compares the electric signals corresponding to changes of dimension in lateral direction with the reference signals.