Permeability is the moisture transmission rate of a material; it is not dependent on the materials' thickness. It is usually measured in perm inches. Permeance is the degree to which a material admits a flow of matter or energy, and it depends on the materials' thickness . The permeance of a vapor barrier is a measure of how fast it lets water vapor through, when its two sides have different partial pressures of water vapor. Permeance is equal to the permeability of the material divided by its thickness. Permeance is usually given in perms, though its SI unit is the kilogram per second per square meter per pascal (kg/s·m²·Pa). This Permeability converter allows you to convert kilogram/pascal-second-sq. meter (kg/(Pa·s·m²)), nanogram/pascal-second-sq. meter (ng/(Pa·s·m²)), permeability (0°C), permeability (23°C), permeability inches (0°C), permeability inches (23°C), among other units related to Permeability.