  We present a calculation of the mass of the 1S0 pseudoscalar anti-b c (Bc)
state using a non-perturbative measurement from quenched lattice QCD. We find
M_Bc = 6.386(9)(98)(15) GeV where the first error is statistical, the second
systematic due to the quark mass ambiguities and quenching and the third the
systematic error due to the estimation of mass of the eta_b.
