Text. We present an effective and practical algorithm for computing Gross-Stark units over a real quadratic base field F. Our algorithm allows us to explicitly construct certain relative abelian extensions of F where these units lie, using only information from the base field. These units were recently proved to always exist within the correct extension fields of F by Dasgupta, Darmon, and Pollack, without directly producing them.Video. For a video summary of this paper, please click here or visit http://www.youtube.com/watch?v=8h1-GW-sTNc.