Studies show that losing up to 100-150 scalp hairs per day is normal but more will be defined as Alopecia which is Hair loss.
Human hair naturally grows in Four phases: anagen, catagen, telogen , and Ketogen.
Anagen is the active or growing phase. Catagen is a fairly short phase of the natural hair cycle during which hairs begin to break down. Telogen is the resting phase. The hairs that are shed daily are often in the resting or late phase in the hair cycle.
Normally, about 10% of the scalp hairs are in the resting or telogen phase at any time. These hairs are not growing and are getting prepared for cyclic shedding.