Knowledge about the creation and diffusion of intrinsic point defects is crucial for devising annealing strategies after irradiation steps as, e.g., implantation. Experimental information can be obtained by observing the appearance and/or disappearance of characteristic electrical, optical or magnetic spectra, however, these have to be first assigned to a given defect. In case of silicon carbide even this very first task has not been accomplished yet in case of the carbon vacancy, with which two different electron spin resonance (ESR) centers (anneling out at very different temperatures) have been identified. Ab initio all-electron supercell calculations have been carried out to determine the hyperfine constants of several defects in 4H-SiC in order to justify the models of the measured ESR signals. The quality of the results were tested on the well-documented case of interstitial hydrogen in silicon.