Greybody factors in black hole physics modify the naive Planckian spectrum that is predicted for Hawking radiation when working in the limit of geometrical optics. We consider the Schwarzschild geometry in (3+1) dimensions, and analyze the Regge-Wheeler equation for arbitrary particle spin s and wave-mode angular momentum ℓ, deriving rigourous bounds on the greybody factors as a function of s, ℓ, wave frequency ω, and the black hole mass m.