UNWRAP is a tool to convert 3D z-stack images of a cylindrical object, e.g. endothelial cells on a glass rod or a blood vessel, into 2D. Conversion of 3D z-stack images into 2D allows quantitative analysis of cell morphology using standard methods. UNWRAP is a Matlab routine that inputs z-stack images and prompts the user to define the circular focal plane, prior to generating the unwrapped image.