Momme is a unit of measurement, much like thread count in Cotton. You can’t use thread count for Silk however, because the silk fibers of Silk are much thinner in diameter than that of cotton so you can easily reach a really high number for a thread count. That’s why momme is used instead. Momme describes the silk’s weight and density.
Momme(mm) is used to measure density of silk fabrics and provide understanding of the quality in a silk fabric. If a piece of silk with the dimensions 100 ft, (30.5 metres), by 45 inches(1.1 metres), weighed 19 pounds (8.62 kg), then the density of the silk fabric would be 19 momme.