The method presented here allows computing the critical current density (Jc) of superconducting materials from its in-field experimentally measured critical current (Ic). This is particularly important for applications like HTS cables for power transmission and fault current limiters, where superconductors experience a local field that is close to the self-field of an isolated conductor. Therefore it is necessary to solve an inverse problem to correct for the contribution derived from the self–field. Here, a method that involves minimum regularization and no human interaction or preconception of the Jc dependence with respect to the magnetic field is presented. This parameter-free approach provides excellent reproduction of experimental data and runs in a few minutes.