Thickness is an important characteristic parameter of electrospun submicron of fiber mats and membranes. The thickness of the mats directly influences performance properties such as permeability and is necessary when determining volumetric parameters such as porosity. Typical electrospun mats are very thin (less than 1 mm) and highly compressive due to the small diameter fibers, both of which make accurate measurements difficult when using conventional methods. An accurate measure of the thickness is desired for characterizing and comparing membrane performances. In this work, a thickness measurement instrument using laser interferometry has been designed to measure electrospun fiber mat thickness. A small disk is used to apply a small (reproducible) force applied across a reasonably small area of the fiber mat. A traversing pin moves to contact the disk and completes an electrical circuit to stop movement and determine the location of the disk relative to a reference plane. The fiber mat thickness is determined by measuring the difference in locations of the disk with and without the fiber mat between the disk and the reference plane. The prototype is simple to operate and user-friendly. Precision and accuracy of the prototype are discussed.