Hair grows in a repeating cycle with three main phases. Anagen is the active growth phase, and on the scalp it lasts roughly 2 to 6 years. Catagen is a brief transition phase of about 2 to 3 weeks where the follicle shuts down. Telogen is a resting phase of roughly 2 to 4 months, after which the hair sheds and the cycle restarts. Scalp hair grows about 1 centimeter per month, which is why a progress photo taken six weeks after starting anything new almost never shows regrowth.
This page explains the cycle and what it means for interpreting your own photo record. If you are tracking hair loss or regrowth over time, the cycle answers most of the timing questions that come up.
| Phase | What happens | Approximate duration (scalp) | Share of hairs at any moment |
|---|---|---|---|
| Anagen (growth) | The follicle actively produces a hair shaft | 2 to 6 years | Roughly 85 to 90 percent |
| Catagen (transition) | The follicle shrinks and detaches from its blood supply | 2 to 3 weeks | About 1 percent |
| Telogen (rest) | The hair is fully formed but not growing; it sheds at the end | 2 to 4 months | Roughly 10 to 15 percent |
What happens in each phase of the hair growth cycle
Anagen: the growth phase
Anagen is when the follicle is doing the actual work. Cells at the base of the follicle divide rapidly and build the hair shaft, which pushes up through the skin at the rate of about 1 centimeter per month. The length of the anagen phase is the main reason some people can grow hair past their waist while others stall at the shoulders. A longer anagen phase simply means more time growing before the hair is released.
On the scalp, anagen runs for years. On eyebrows, arms, and legs it runs for only weeks or months, which is why body hair stays short. The follicles are the same machinery, but their internal clocks are set differently.
For tracking purposes, anagen is the phase that matters most. Any intervention that affects hair has to push hairs through this phase to produce visible length or density. That applies to treatments, supplement changes, and shifts in an underlying condition alike. It takes time by definition.
Catagen: the transition phase
Catagen is a short shutdown. The follicle stops producing the hair, the lower part of the follicle shrinks, and the hair becomes anchored in place by a club-shaped root rather than an active connection. Only a small fraction of hairs are in catagen at any moment, and the phase is over in a few weeks.
You will never observe catagen in a photo. Its relevance is that it sits between growth and rest, so a hair that stops growing today will not shed for another few months. This delay is the reason changes in shedding lag so far behind whatever caused them.
Telogen: the resting phase
In telogen the hair is finished but not yet gone. It sits in the follicle for roughly 2 to 4 months before shedding. Shedding itself is sometimes called exogen, and many sources fold it into telogen as its final step. Either way, the hair that falls out was already dead weight for months before it left your head.
This is the phase that causes the most confusion for people tracking hair loss. When you see a hair in the shower drain, that hair stopped growing months ago. The shedding you notice today reflects a signal your body sent in the past, not something that happened this week.
How fast does hair actually grow
Scalp hair grows about 1 centimeter per month, or roughly 0.3 to 0.4 millimeters per day. Over a year that is around 12 centimeters of length for a healthy anagen hair. Individual variation exists, and growth rate is influenced by age, genetics, nutrition, and overall health.
Density changes are even slower to see than length changes. A follicle that re-enters anagen first produces a hair so fine it may be invisible for weeks. That hair then has to thicken and lengthen before it contributes anything you can photograph. A practical implication is that density improvements in photos tend to appear in the 3 to 6 month window at the earliest, and often later.
Why your progress photos lag behind reality
The cycle creates a built-in delay between a change in your body and a change in your photos. Consider the sequence for a hair that responds to something new you started today.
- The follicle has to shift into or extend anagen, which does not happen instantly.
- The new hair has to emerge from the scalp, which takes weeks on its own.
- The hair has to gain enough length and pigment to be visible in a photo, which takes more weeks.
- Meanwhile, hairs already in telogen will shed on their old schedule regardless of what you are doing now.
This is why a photo comparison at week 6 tells you almost nothing about regrowth. It can tell you whether shedding has changed, and it can confirm your photo setup is consistent. It cannot show new growth that has not had time to surface.
It is also why the first months of any hair-related change can look worse before they look better. Hairs that were pushed into telogen by a past event shed on a delay, and those sheds land in your photo record weeks or months after the trigger. If you compare photos at week 8 and see thinning, you are looking at a message from months ago.
What shedding phases mean for your photo log
Shedding is a normal output of the cycle. Every scalp loses dozens to about a hundred telogen hairs per day as part of ordinary turnover. A shed is only meaningful relative to your own baseline, and even then a temporary increase can reflect a stressor from two or three months earlier rather than a current problem.
For your photo log, this argues for two things. First, do not react to a single shedding week. Note it in your check-in log with the date, then keep your photo schedule unchanged. Second, when you do see a change in a photo comparison, think about what was happening 2 to 4 months before, not what happened last week. That is the window in which the hairs currently shedding received their signal.
A realistic timeline for photo comparisons
Given the cycle, a sensible expectation for a photo record looks like this. Weeks 0 to 6 are a baseline and consistency-check period. Months 2 to 3 are when shedding changes, if any, become visible, and they may look negative. Months 3 to 6 are the earliest window where density changes could plausibly show. Months 6 to 12 are where meaningful comparisons become possible, because hairs that responded early have had time to emerge and add visible length.
This is not a claim about any treatment. It is arithmetic from the cycle itself. A hair needs months to grow, and a photo needs visible hairs to change.
What you can track over time
The cycle suggests specific things worth recording in a structured way.
- Fixed-interval photos. Monthly or quarterly photos at the same angles, distance, and lighting beat sporadic shots. A schedule keeps you from over-checking during the noisy early months.
- Shedding notes with dates. A rough daily shed count or a simple high, normal, or low rating lets you connect a shed to events from 2 to 4 months prior.
- Setup changes. Record anything that changes between photos, including new products, haircuts, lighting, or camera position. A haircut alone can make a comparison useless.
- Widening parts or specific thinning spots. These are more informative than overall impressions because they can be framed identically each time.
Consistent framing is what makes month 6 comparable to month 0. Before worrying about what your photos show, confirm they are actually comparable. The same angle, distance, exposure, and hair preparation matter as much as the hair itself.
How to build a photo routine around the cycle
Start with a baseline set of photos taken before any change, using a fixed framing reference so future shots line up. Then set check-in dates at intervals long enough for the cycle to produce visible change, which means monthly at most and quarterly for length tracking. Between check-ins, keep a simple log of shedding and any changes to your routine.
At each check-in, compare the new photos against the baseline rather than against last month. Short-interval comparisons amplify noise from lighting and hair arrangement. Long-interval comparisons against a stable baseline are where real change becomes visible.
FAQ
How long does hair take to grow back after shedding?
A shed telogen hair is replaced by a new anagen hair, but that hair takes weeks to emerge and months to become visible in photos. Expect at least 3 to 6 months before a photo comparison could plausibly show replacement density.
Can a progress photo at week 6 show regrowth?
Almost never. New hairs need time to enter anagen, emerge, and gain visible length. A week 6 photo is useful for confirming your setup and checking for shedding changes, not for judging regrowth.
Why does shedding increase months after a stressful event?
Stressors can push hairs from anagen into telogen. Those hairs then rest for 2 to 4 months before shedding, so the visible shed appears well after the trigger. This pattern is called telogen effluvium.
How often should I take progress photos?
Monthly is a reasonable interval for density tracking, and quarterly works for length. More frequent photos mostly capture lighting and styling differences rather than real change.
Does hair grow at the same rate for everyone?
No. The average is about 1 centimeter per month on the scalp, but rate varies with age, genetics, and health. Your own baseline photos are a better reference than any population average.