Milne, a routine for the numerical solution of Milne’s problem. The routine Milne provides accurate numerical values for the classical Milne’s problem of neutron transport for the planar one speed and isotropic scattering case. The solution is based on the case eigen-function formalism. The relevant $X$ functions are evaluated accurately by the double exponential quadrature. The calculated quantities are the extrapolation distance and the scalar and the angular fluxes. Also, the $H$ function needed in astrophysical calculations is evaluated as a byproduct.