Abstract Spectroscopic constants and molecular properties of the diatomic carbides BeC, BC + , BC, NaC, and MgC in their ground states have been studied in detail using hybrid HF/DF B3LYP method. The effect of basis set on spectroscopic constants and molecular properties have been studied systematically with the improvement of the quality of the basis set from cc-pVDZ to cc-pV5Z. These results have been extrapolated to the complete basis set (CBS) limit. The spectroscopic constants of these diatomic carbides agree very well with the experimental and theoretical results wherever available for comparison. Most of the spectroscopic constants of BC, BC + , and NaC and the molecular properties of these carbides are first reported.