A magnetic confinement system in the form of a stuffed toroidal line-cusp (Tormac) is proposed as the basis for a thermonuclear reactor. The interior (stuffing) region is assumed to consist of closed of closed magnetic flux surfaces and a Maxwellian DT plasma at high levels of beta. The particles in the surrounding sheath, on the other hand, are mirror-confined on open field lines and thus are lost into a divertor region at the ion-ion collision rate. The confinement based on this assumption is given by nτ ∝ rp BTi, where rp denotes the plasma minor radius. In this paper, power gain and net output of Tormac reactors for a wide range of parameters are calculated. The net power gain QE, the gross electric output power/circulating electric power, is found to have values between 2 and 10 for reasonable reactor dimensions and very modest magnetic field strengths. For example, a plant yielding 500 MW net electrical power using ions at 40 keV thermal energy and a magnetic field of 40 kG would require a plasma of minor radius rp = 1 m and a major radius of 5 m. Q enhancement by direct recovery of particle energy has not yet been included.