Formation and migration energies, elastic dipole and relaxation volume tensors of nano-defects are the parameters that determine the rates of evolution of microstructure under irradiation and the magnitude of macroscopic elastic stresses and strains resulting from the accumulation of defects in materials. To find accurate values of these parameters, we have performed density functional theory simulations of self-interstitial and vacancy defects in all the body-centred cubic metals, including alkaline metals (Li, Na, K, Rb and Cs), alkaline-earth metal (Ba), non-magnetic bcc transition metals (V, Nb, Mo, Ta andW), and magnetic transition metals (Cr and Fe), correcting the computed values for the effect of finite cell size and periodic boundary conditions. The lowest energy structure of a self-interstitial atom defect is universal to all the non-magnetic bcc metals, including metals of Group 1 and 2 of the Periodic Table, and has the <111> symmetry. The only exceptions are the <110> self-interstitial defect configuration in Fe, and a <11ξ> configuration in Cr. We have also computed elastic dipole tensors and relaxation volumes of self-interstitial and vacancy defects in all the bcc metals and explored how elastic relaxation parameters evolve along defect migration pathways.