GrayHawk calculates the gray-body factors of massless fields propagating around spherically symmetric black holes. It uses a Mathematica framework to compute transmission coefficients for spins s = 0, 1/2, 1, 2 across specified angular modes l given a user-defined metric and parameter set. The code includes pre-loaded support for seven black-hole metrics and enables users to add new metrics via its modular structure. GrayHawk streamlines modeling of Hawking radiation and grey-body spectra, making it applicable to a variety of theoretical scenarios in gravitational physics.