Synchrotron white beam x-ray reticulography was used to quantitatively map the residual stress/strain in SiC wafers. The basic principle of our study is that there exists a relationship between the stress state in a crystal and the local lattice plane orientation and that this relationship can be exploited in order to determine the full strain tensor as a function of position inside the crystal. The theoretical background of the stress mapping using synchrotron white beam x-ray reticulography is introduced and it is based on the change of plane normal of the lattice plane due to the distortion associated with the residual strain. The stress mapping of a crystal region from a commercial 4H silicon carbide wafer has been studied using this technique and the results are discussed. This technique can in principle be used in any single crystal material.