We construct a model for black hole formation in galactic bulges. The initial state is a slowly rotating isothermal sphere, with an effective transport speed aeff and rotation rate Ω. The black hole mass is determined when the centrifugal radius of the collapse flow exceeds the capture radius of the central black hole. This model reproduces the observed correlation between black hole masses and galactic velocity dispersions, Mbh ≈ 108 M × (σ/200 km s-1)4, where σ = aeff. This model also predicts the ratio μB of black hole mass to host mass: μB ≈ 0.004(σ/200 km s-1).