Relaxed (force-free) toroidal plasmas ('Taylor states') are of interest in fusion physics. The zero flux condition yields eigenvalues connected with the maximum toroidal current. Up to now, these eigenvalues have only been calculated for infinite aspect ratios and circular cross-sections or for rectangular cross-sections of the torus. Here, the zero flux and some zero field eigenvalues are calculated for toroids of arbitrary aspects ratios and arbitrary cross-sections such as circles, ellipses or Cassini curves.