ERKALE is a quantum chemistry program used to solve the electronic structure of atoms, molecules and molecular clusters. It was originally developed at the University of Helsinki for the computation of x-ray properties, such as ground-state electron momentum densities and Compton profiles, and core (x-ray absorption and x-ray Raman scattering) and valence electron excitation spectra of atoms and molecules. Subsequently, it has gained unique functionalities for basis set development as well as self-interaction corrected density-functional theory calculations.