Anagen:telogen ratio (12:1 to 5:1)
Your scalp is a factory where 9 in 10 follicles are growing. When that math flips, you shed.
Grounded in the research on Hair follicle
What even is the anagen:telogen ratio?
Every scalp follicle cycles through phases: anagen (active growth), catagen (a ~2-3 week regression), and telogen (resting, ~3 months). The ratio is how many anagen follicles you have for every telogen one. On a healthy scalp it sits between 12:1 and 5:1 - meaning roughly 85-90% of your ~100,000 follicles are actively growing at any moment, and only 10-15% are resting. That dominance is why you have a full head of hair instead of patchy clumps.
Why is anagen so long and telogen so short?
Anagen on the scalp lasts 2-7 years, which is why head hair can grow to your waist. Telogen only lasts ~3 months. Long growth phase plus short rest phase equals a high ratio. Body hair has the opposite setup: short anagen, so leg and arm hair maxes out at a few centimeters and never grows long. Same follicle machinery, different phase durations. The ratio is just a snapshot of those clocks running out of sync across all your follicles.