The contact block reduction (CBR) method is a variant of the nonequilibrium Green’s function formalism and can be used to describe quantum transport in the ballistic limit very efficiently. We present a numerical implementation of a charge self-consistent version of the CBR algorithm. We show in detail how to calculate the electronic properties of open quantum systems such as the transmission function, the local density of states and the carrier density. Several 1D and 2D examples are provided to illustrate the key points. The CBR method is a very powerful tool to tackle the challenge of calculating transport in the ballistic limit for 3D devices of arbitrary shape and with an arbitrary number of contacts.