Microfiber is defined as a fiber that is 1 denier or less. What is a denier? It’s a measurement of fineness equal to a unit of fiber that weighs one gram for each 9000 meters -- meaning it is really small. To put it in perspective, microfiber is 1/100 the diameter of a human hair and 1/20 the diameter of a strand of silk. One square inch of microfiber cloth has approximately 200,000 fibers.