How fast do nails and hair grow?
Hair grows about 1 cm (0.4 inch) a month (Natarelli, 2023), fingernails 3.5 mm a month and toenails 1.6 mm (Yaemsiri, 2010). A fingernail fully grows out in 4 to 6 months, a toenail in 12 to 18 months (to be verified).
Schematic drawing, not to scale. The growth lines are calculations using the published average speeds; the dotted shedding and density curves are estimates.
How fast does hair grow?
Four hairs in their follicles, seen in cross-section under the skin. Choose a situation, then tap a label on the drawing to find out what it is.
Sources: hair growth and cycle (Natarelli et al., J Clin Med, 2023); normal shedding and shedding after a shock (American Academy of Dermatology; Malkud, J Clin Diagn Res, 2015). Drawing not to scale; scene durations: estimates.
Keyboard: 1 2 situations, Space pause, L slow motion, R restart, ← → previous or next step.
How fast do nails grow?
A fingertip seen from the side, with its nail. Choose a situation, then tap a label on the drawing to find out what it is.
Sources: nail growth speed in 22 young adults (Yaemsiri et al., J Eur Acad Dermatol Venereol, 2010); Beau's lines (Braswell et al., J Am Acad Dermatol, 2015). Drawing not to scale; scene durations: estimates; distances on the nail: calculations.
Keyboard: 1 2 situations, Space pause, L slow motion, R restart, ← → previous or next step.
Frequently asked questions about nails and hair
How many centimeters does hair grow per month?
Scalp hair grows about 1 cm (0.4 inch) a month, roughly 12 cm (about 5 inches) a year (Natarelli, 2023). This is an average: the speed varies from person to person, with age and by area of the body. A hair only grows during its growth phase, anagen, which lasts 2 to 8 years on the scalp: that is what sets the maximum length it can reach.
Why do toenails grow more slowly?
In a study of 22 young adults, fingernails grew 3.47 mm a month and toenails 1.62 mm, about half as fast (Yaemsiri, 2010). The exact reason is not well known: slower blood flow in the feet and less-used nails have been suggested. On the hand, the little fingernail is the slowest; on the foot, the big toenail is the fastest.
How many hairs do you lose a day?
Losing 50 to 100 hairs a day is normal (American Academy of Dermatology). The scalp has about 100,000 hairs, and about 9% are resting at any given time (Natarelli, 2023): these are the ones that fall out, pushed out by a new hair. You often notice more on wash days, because hairs that were ready to fall all come out together.
Why does hair fall out after giving birth?
During pregnancy, many hairs stay longer in the growth phase. After giving birth, they go into rest at the same time and fall out a few months later: this is telogen effluvium (Malkud, 2015). A high fever, surgery, a crash diet or major stress can do the same. Shedding usually stops within 3 to 6 months, and fullness most often returns in 6 to 9 months (American Academy of Dermatology).
What do Beau's lines on the nails mean?
A Beau's line is a groove running across the nail. It appears when the matrix, the area that makes the nail, has slowed down, for example after a serious illness, a high fever, surgery or certain medicines (Braswell, 2015). Since a fingernail grows about 3.5 mm a month, a groove 7 mm from the base dates back about 2 months (calculation). If it keeps coming back with no known cause, it is best to talk to a doctor.
True or false?
Cutting your hair makes it grow faster.
False. Hair is made in the bulb, under the skin; the part you cut is no longer alive. Trimming damaged ends does not change the growth speed, about 1 cm (0.4 inch) a month (Natarelli, 2023).
Fingernails grow faster than toenails.
True. In 22 young adults, fingernails grew 3.47 mm a month and toenails 1.62 mm, about half as fast (Yaemsiri, 2010).
Losing 100 hairs a day is a sign of a problem.
False. Losing 50 to 100 hairs a day is normal (American Academy of Dermatology). Much heavier shedding, hair loss in patches, or shedding that lasts more than 6 months is worth seeing a doctor about.
This page as text
The same information as the charts, to read without animation: for each chart, the values at the main moments, then the notes with their level of evidence.
How much do hair and nails grow in a month?
A hair gains about 1 cm a month, a fingernail 3.5 mm, a toenail 1.6 mm. These lines are a calculation using the average speeds. Top of the chart: 18 cm.
| Months of growth, years of a hair cycle, or months after a shock | Hair (calculation) (dotted) | Fingernail (calculation) (dotted) | Toenail (calculation) (dotted) | What happens |
|---|---|---|---|---|
| start | 0 | 0 | 0 | 0 months: hair 0 cm, fingernail 0 mm, toenail 0 mm (calculation) |
| 3 mo | 17 | 6 | 3 | nths: hair 3 cm, fingernail 10.4 mm, toenail 4.9 mm (calculation) |
| 6 mo | 33 | 12 | 5 | nths: hair 6 cm, fingernail 20.8 mm, toenail 9.7 mm (calculation) |
| 9 mo | 50 | 17 | 8 | nths: hair 9 cm, fingernail 31.2 mm, toenail 14.6 mm (calculation) |
| 12 mo | 67 | 23 | 11 | nths: hair 12 cm, fingernail 41.6 mm, toenail 19.4 mm (calculation) |
| 15 mo | 83 | 29 | 14 | nths: hair 15 cm, fingernail 52.1 mm, toenail 24.3 mm (calculation) |
| 18 mo | 100 | 35 | 16 | nths: hair 18 cm, fingernail 62.5 mm, toenail 29.2 mm (calculation) |
Key points
- Hair: 1 cm a month (Throughout, Shown in humans)
A hair grows about 1 cm a month, roughly 12 cm (about 5 inches) a year, as long as it is in its growth phase. Source: Natarelli, Gahoonia and Sivamani, "Integrative and mechanistic approach to the hair growth cycle and hair loss," J Clin Med, 2023 - Nails: 3.5 mm and 1.6 mm a month (Throughout, Shown in humans)
In 22 young adults who marked their nails with a file, fingernails grew 3.47 mm a month and toenails 1.62 mm, with no difference between the right and left hand. Source: Yaemsiri, Hou, Slining and He, "Growth rate of human fingernails and toenails in healthy American young adults," J Eur Acad Dermatol Venereol, 2010 - Not all at the same speed (Up to 6 months, Shown in humans)
The little fingernail grew the slowest of the hand, the big toenail the fastest of the foot. Being young, being male or biting your nails went with slightly faster growth, but without a clear difference. Source: Yaemsiri, Hou, Slining and He, "Growth rate of human fingernails and toenails in healthy American young adults," J Eur Acad Dermatol Venereol, 2010 - A new fingernail in 4 to 6 months (From 4 to 6 months, Hypothesis)
At 3.5 mm a month, a fingernail grows out completely in about 4 to 6 months, depending on its length (to be verified). - A new toenail in 12 to 18 months (From 12 months, Hypothesis)
Twice as slow, toenails take about 12 to 18 months to grow out (to be verified). That is why a damaged toenail takes so long to look normal again. - Faster than before? (From 6 months, Shown in humans)
These speeds are faster than those measured a few decades ago, and no one really knows why. Source: Yaemsiri, Hou, Slining and He, "Growth rate of human fingernails and toenails in healthy American young adults," J Eur Acad Dermatol Venereol, 2010
Why doesn't hair grow forever?
Each hair grows for 2 to 8 years, rests for about 3 months, then falls out, and a new one takes its place. Maximum length depends on how long the growth phase lasts. These curves are a calculation; top of the chart: 80 cm.
| Months of growth, years of a hair cycle, or months after a shock | Short-cycle hair, 2 years (calculation) (dotted) | Long-cycle hair, 6 years (calculation) (dotted) | What happens |
|---|---|---|---|
| start | 0 | 0 | 0 yr: short-cycle hair 0 cm (growing), long-cycle hair 0 cm (growing) (calculation) |
| 1 yr | 15 | 15 | short-cycle hair 12 cm (growing), long-cycle hair 12 cm (growing) (calculation) |
| 2 yrs | 30 | 30 | short-cycle hair 24 cm (transition), long-cycle hair 24 cm (growing) (calculation) |
| 3 yrs | 10 | 45 | short-cycle hair 8.4 cm (growing), long-cycle hair 36 cm (growing) (calculation) |
| 4 yrs | 26 | 60 | short-cycle hair 20.4 cm (growing), long-cycle hair 48 cm (growing) (calculation) |
| 5 yrs | 6 | 75 | short-cycle hair 4.8 cm (growing), long-cycle hair 60 cm (growing) (calculation) |
| 6 yrs | 21 | 90 | short-cycle hair 16.8 cm (growing), long-cycle hair 72 cm (transition) (calculation) |
| 7 yrs | 2 | 10 | short-cycle hair 1.2 cm (growing), long-cycle hair 8.4 cm (growing) (calculation) |
| 8 yrs | 16 | 26 | short-cycle hair 13.2 cm (growing), long-cycle hair 20.4 cm (growing) (calculation) |
Key points
- Anagen: growth (Up to 2 years, Shown in humans)
On the scalp, the growth phase, called anagen, lasts 2 to 8 years. On the eyebrows, it lasts only 2 to 3 months: that is why they stay short. Source: Natarelli, Gahoonia and Sivamani, "Integrative and mechanistic approach to the hair growth cycle and hair loss," J Clin Med, 2023 - Catagen, then telogen (From 2 to 2.3 years, Shown in humans)
The hair stops for about 2 weeks (catagen), then rests for 2 to 3 months (telogen) before falling out. About 9% of hairs are resting at any given time. Source: Natarelli, Gahoonia and Sivamani, "Integrative and mechanistic approach to the hair growth cycle and hair loss," J Clin Med, 2023 - 100,000 hairs, each on its own schedule (Throughout, Shown in humans)
A scalp has about 100,000 hairs, each with its own cycle: they never all fall out at the same time. Source: Natarelli, Gahoonia and Sivamani, "Integrative and mechanistic approach to the hair growth cycle and hair loss," J Clin Med, 2023 - How many fall out each day? (From 2 years, Shown in humans)
Losing 50 to 100 hairs a day is normal, according to the American Academy of Dermatology; other authors go as high as 100 to 150. Source: American Academy of Dermatology, "Do you have hair loss or hair shedding?" - Maximum length (From 4 years, Hypothesis)
At 12 cm a year, 2 years of growth give about 24 cm and 8 years about 96 cm (calculation). That is why some people struggle to grow very long hair.
Why does hair fall out a few months after a fever or giving birth?
A shock pushes many hairs into rest at the same time; they fall out 2 to 3 months later, then grow back. On the nail, a groove forms and moves forward as the nail grows. Shedding and density: estimates; groove: calculation.
| Months of growth, years of a hair cycle, or months after a shock | Hair shedding (estimated) (dotted) | Hair on the head (estimated) (dotted) | Nail groove, way to the tip (calculation) (dotted) | What happens |
|---|---|---|---|---|
| shock | 20 | 100 | 0 | 0 months after the shock: shedding normal, hair on the head 100% (estimates), nail groove 0 mm from the base (calculation) |
| 2 mo | 32 | 100 | 40 | nths after the shock: shedding heavier than usual, hair on the head 100% (estimates), nail groove 6.9 mm from the base (calculation) |
| 3 mo | 100 | 92 | 60 | nths after the shock: shedding at its peak, hair on the head 92% (estimates), nail groove 10.4 mm from the base (calculation) |
| 4 mo | 72 | 82 | 80 | nths after the shock: shedding heavy, hair on the head 82% (estimates), nail groove 13.9 mm from the base (calculation) |
| 6 mo | 24 | 82 | 100 | nths after the shock: shedding normal, hair on the head 82% (estimates), nail groove gone with trimming (calculation) |
| 8 mo | 20 | 92 | 100 | nths after the shock: shedding normal, hair on the head 92% (estimates), nail groove gone with trimming (calculation) |
| 10 mo | 20 | 98 | 100 | nths after the shock: shedding normal, hair on the head 98% (estimates), nail groove gone with trimming (calculation) |
| 12 mo | 20 | 100 | 100 | nths after the shock: shedding normal, hair on the head 100% (estimates), nail groove gone with trimming (calculation) |
Key points
- Nothing shows at first (Up to 2 months, Shown in humans)
High fever, childbirth, surgery, a crash diet or major stress: many hairs go into rest at the same time. They only fall out 2 to 3 months later; this is telogen effluvium. Source: Malkud, "Telogen effluvium: a review," J Clin Diagn Res, 2015 - The shedding (From 2 to 4 months, Shown in humans)
Hair then falls out more than usual, in handfuls when washing, but usually no more than half of the hair. Source: Malkud, "Telogen effluvium: a review," J Clin Diagn Res, 2015 - Beau's lines (Up to 5 months, Shown in humans)
On the nails, a serious illness, surgery, some medicines or a shock can slow the matrix: a groove appears across the nail, then moves forward as it grows. Source: Braswell, Daniel and Brodell, "Beau lines, onychomadesis, and retronychia: a unifying hypothesis," J Am Acad Dermatol, 2015 - Dating the shock (Up to 5 months, Hypothesis)
The groove moves forward about 3.5 mm a month: 7 mm from the base, the shock was about 2 months ago (calculation). It is trimmed away once the nail has grown out, in 4 to 6 months (to be verified). Source: Yaemsiri, Hou, Slining and He, "Growth rate of human fingernails and toenails in healthy American young adults," J Eur Acad Dermatol Venereol, 2010 - It grows back (From 6 months, Shown in humans)
Shedding usually stops within 3 to 6 months, and hair gets back its usual fullness in 6 to 9 months according to the American Academy of Dermatology. For visible length, it sometimes takes 12 to 18 months. Source: American Academy of Dermatology, "Do you have hair loss or hair shedding?" - If it lasts (From 6 months, Shown in humans)
Shedding that lasts more than 6 months is called chronic and is worth a visit to the doctor. Source: Malkud, "Telogen effluvium: a review," J Clin Diagn Res, 2015 - Estimated curves (Throughout, Hypothesis)
The shape of the shedding and density curves follows the published timing; their level varies a lot from person to person.
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