In physiology, filtration coefficient (Kf) is the product of a biological membrane's permeability to water and the surface area of the membrane. Typical units of Kf are mL/min/mmHg. The rate of filtration across the membrane is, by definition, the product of Kf and the net filtration pressure across the membrane.[1] [2] Kf is frequently applied to the glomerular capillaries, which filter water into Bowman's capsule to form urine. Typically, in an adult human, the net filtration pressure is 10mmHg and Kf 12.5mL/min/mmHg, giving a glomerular filtration rate (GFR) of 125mL/min. A decrease in Kf due to reduced number of glomeruli or reduced permeability will reduce the GFR at a given filtration pressure[3]