Fiber bonding ability is highly affecting the structure, strength, and surface of printing papers, and is very much dependent on the inhomogeneity of the raw material; a mixture of early- and latewood fibers. However, until recently, only average values have been used to evaluate fiber bonding ability. In this paper, a method to measure the distribution of fiber bonding ability, BIN, is presented. BIN, Bonding Indicator, is calculated by combining external fibrillation and collapse resistance index (calculated from fiber wall thickness and fiber width) from optical measurements.