How Fast Does Hair Grow: Daily, Weekly and Monthly Timeline

Scalp hair grows about 0.3 to 0.4 mm a day, which adds up to roughly 1 cm a month and about 12 cm a year. The exact speed varies with age, ancestry and hair colour, and each follicle only adds length during its active growth phase.

Those averages hide a lot of variation. One person's hair can grow noticeably faster than another's, and the same scalp grows at slightly different speeds in different areas. This guide covers:

• the measured growth rates, by day, week and month
• what changes the speed from one person to the next
• the three phases of the hair growth cycle
• when slow growth or heavy shedding is worth a medical check

Hair Growth Stages

Not every hair on your head is growing at the same time. Each follicle runs through its own cycle of growth, regression and rest, and the cycles are not in step with each other. That is why you never lose all your hair at once, and why the scalp keeps a fairly even look.

At any one moment, most scalp hairs are in the growing stage. Two sources give similar shares:

Only the anagen hairs add length. So when people ask how fast hair grows, the honest answer is: the growing ones lengthen by about 0.3 mm a day, while one hair in ten or so is resting and not growing at all. The details of each phase are set out further down, in the section on the hair growth cycle.

How Fast Does Hair Grow?

A review in Deutsches Ärzteblatt International gives the standard clinical figure: scalp hair grows about 0.3 mm a day, or about 1 cm a month. Cleveland Clinic gives the same 1 cm a month. Studies that measure growth directly show how much the figure moves between groups.

Even inside one group, the spread is wide. In the African volunteers, individual rates ranged from 0.150 to 0.363 mm a day. A larger study by Loussouarn and colleagues, covering 2,249 young adults from 24 ethnic groups, found that African hair grew more slowly on average and Asian hair grew faster.

Most adult figures on this page come from a phototrichogram. A 2022 study in Clinical, Cosmetic and Investigational Dermatology describes it as a noninvasive technique that pairs a digital video microscope with image analysis. The African study used it to record density, the share of resting hairs and growth rate in three areas of the scalp.

When to See a Healthcare Provider?

Slow growth on its own is rarely a medical problem. The bigger signals are changes in how much hair you lose and where. The American Academy of Dermatology says shedding 50 to 100 hairs a day is normal and lists situations that can trigger heavier shedding:

• losing 20 pounds or more
• giving birth
• a lot of ongoing stress
• a high fever, an operation or recovery from illness
• stopping birth control pills

The academy notes that this type of shedding often shows up a few months after the event and usually settles, with hair tending to regain its fullness within six to nine months. Hair loss is different: something stops the hair from growing, as in hereditary hair loss, and it does not return until the cause is treated.

See a dermatologist if shedding is clearly heavier than usual, if it goes on for months, if you see patches or a widening part, or if you think a medicine might be involved. The academy advises not stopping a prescribed treatment on your own, and says the sooner treatment begins, the better the outlook.

How Much Does Hair Grow in a Week?

At 0.3 to 0.4 mm a day, scalp hair grows about 2 to 3 mm in a week. A week of growth is hard to see on long hair but easy to see on a very short cut.

Using the measured averages, a week of growth looks like this:

• White adults, 0.396 mm a day: about 2.8 mm
• Clinical average, 0.3 mm a day: about 2.1 mm
• African adults, 0.256 mm a day: about 1.8 mm

For someone with a 3 mm buzz cut, one week can nearly double the length. For someone with shoulder-length hair, the same 2 mm disappears into the length. Our guide to how many hairs are on the human head explains why density, not length, decides how full hair looks.

How Much Does Hair Grow Every Day?

Every day, each growing hair adds about 0.3 to 0.4 mm. Researchers usually express this in micrometres, where 1 mm equals 1,000 micrometres, so the studies above report figures such as 396 or 256 micrometres a day.

The growth happens deep in the skin, not at the tip. New cells are made in the hair bulb at the base of the follicle and push the older part of the hair upward. A review by Tobin in the International Journal of Trichology notes that almost all of the keratin-making cells in a growing bulb are dividing at any one time, at a rate second only to bone marrow and the lining of the gut. Our page on the hair bulb explains that part of the follicle.

Because growth starts at the base, the hair nearest the scalp is always the newest. The ends are the oldest part, which is why they look drier and more worn, as our hair shaft anatomy guide explains.

Daily Hair Growth: What Changes the Rate

Several factors are linked to faster or slower daily growth in the studies we reviewed:

• Age: infants under 1 year grew hair more slowly than children aged 2 to 5 in the 2024 study of 266 preschool children.
• Hair colour: dark-haired children grew hair faster than light-haired children in the same study.
• Ancestry: African hair grew more slowly and Asian hair faster in the 24-group study.
• Scalp area and sex: the 24-group study linked differences to both, while the smaller African study found no difference by sex or scalp area.

In the children's study, the factors that predicted growth rate were age, height, hair pigment and the protein content of the hair. Sex was not among them. For adult men and women, the large study reported some differences by sex, but the abstract does not give a single figure for each, so we do not quote one.

What does not appear in these studies is just as useful. None of them shows that cutting hair makes it grow faster. Trimming removes worn ends from the oldest part of the hair; it does not change what the follicle does.

Hair Growth Per Day in Inches

For readers who think in inches, 1 inch is 25.4 mm. The daily figure is tiny:

• 0.3 mm a day is about 0.012 inch
• 0.4 mm a day is about 0.016 inch
• 1 cm a month is about 0.4 inch
• 12 cm a year is about 4.7 inches

So the common rule of thumb of about half an inch a month is a little generous for the average adult. It fits the faster end of the measured range, such as the white adults in the 2001 study, better than the slower end.

How Much Does Hair Grow in 3 Months?

In three months, scalp hair grows about 3 cm, or a little over 1 inch. That is enough to grow out a short haircut or to see clear new length at the roots after colouring.

Three months is also an important point after a hair transplant, and the timeline there is different. The American Academy of Dermatology explains that transplanted hairs usually fall out within two to eight weeks, that the area can look thinner around the third month, and that most people see new growth between six and nine months, with some waiting 12 months. Our hair transplant recovery timeline walks through each stage.

The reason is the growth cycle again. The transplanted hairs are shed first, the follicles then start a new growing phase, and only after that does length build at the usual 1 cm or so a month.

How Much Does Hair Grow in 2 Days?

In two days, hair grows about 0.6 to 0.8 mm. That is less than one millimetre, so on most people it cannot be seen without measuring.

Short timeframes like this are why studies measure growth with magnified images rather than by eye. On a full head of hair, a change of under a millimetre is lost in the length, the curl and the way hair falls.

How Much Does Hair Grow in 4 Days?

In four days, hair grows about 1.2 to 1.6 mm. On a freshly shaved or closely clipped scalp, that is the point where new stubble becomes easy to see and feel.

If you want to check your own rate, a rough home method is simple:

• clip or shave a small patch somewhere discreet
• photograph it next to a ruler on day one
• photograph it again under the same light on day four or seven
• compare the length, then divide by the number of days

The result will be rougher than a clinical measurement, but it shows whether your hair sits near the averages above.

Hair Growth Cycle

The growth cycle explains why hair length has a natural limit and why shedding is normal. The 2016 review in Deutsches Ärzteblatt International and Cleveland Clinic give slightly different ranges for each phase, and both are shown below.

Anagen

Anagen is the growing phase. The Deutsches Ärzteblatt review gives 2 to 6 years for scalp hair, and Cleveland Clinic gives 2 to 7 years. Tobin's review describes a usual length of 3 to 5 years.

The length of anagen sets how long hair can get. At about 1 cm a month, a 3 year anagen phase allows roughly 36 cm of growth before the hair stops, and a 6 year phase allows roughly 72 cm. This helps explain why some people can grow very long hair while others find it stops at a shorter length.

Catagen

Catagen is a short transition. The Deutsches Ärzteblatt review gives 1 to 2 weeks, and Cleveland Clinic about 2 weeks. A 2020 study in the Annals of Dermatology notes that protein and pigment production stop in this phase, and the review in Biology describes about two thirds of the lower follicle breaking down while the dermal papilla stays intact.

Telogen

Telogen is the resting phase. The Deutsches Ärzteblatt review gives 2 to 4 months, and Cleveland Clinic up to 4 months. The 2020 study adds that a resting hair does not fall out at once but stays in the follicle for a while before it is shed, and the follicle then starts a new growth phase.

The Deutsches Ärzteblatt review also notes that a share of telogen hairs above 20% points to increased shedding. That is one of the measures a dermatologist can use when shedding seems heavy.

Frequently Asked Questions

Want to Know What Your Hair Is Doing?

If your hair seems to grow but the scalp still looks thinner each year, the issue is usually not speed. It is how many follicles are still producing hair. A photo review can show where density has dropped. Send:

• the front hairline, hair pushed back
• the top of the head, from above
• the back and sides, where donor hair sits

Then ask for a free hair analysis. If a transplant is suitable, our hair transplant cost page lists the all-inclusive packages from $2,550 to $4,500.

Medical disclaimer: This article is for informational purposes only and is not medical advice. Individual results and recovery vary from person to person. Always follow the written aftercare plan from your own medical team.