How Fast Does Hair Grow? What a Centimetre a Month Means for Your Cut

Scalp hair grows about a centimetre every month

The widely quoted dermatology figure is about 1 cm of scalp growth per month, and health sources put the yearly total at 4 to 6 inches (10 to 15 cm). That breaks down to roughly a third of a millimetre a day, too little to see in the mirror from one morning to the next.

Not every hair on your head is growing at once. Each follicle cycles through a long growth phase (anagen) that lasts about two to seven years, a short transition of about two weeks, and a resting phase of up to four months before the hair sheds. Losing 50 to 100 hairs a day is normal and simply means old hairs are making room for new ones.

What speeds growth up or slows it down?

Genetics sets most of your pace, and nothing sold in a bottle overrides it. Around that baseline, a handful of factors nudge the number up or down.

• Age: growth tends to be quicker in your teens and twenties and gradually slows later on.
• Nutrition: very low protein, iron or calorie intake can slow growth and thin the hair.
• Scalp health: an itchy, flaky, inflamed scalp is not a good environment for growth.
• Illness, major stress and some medications can push more hairs into the resting phase at once.
• Body site: beard, eyebrow and body hair each follow their own cycle, so they do not match your scalp.

How a month of growth changes different cuts

The same centimetre looks completely different depending on where your hair started. On a bald fade the bottom of the head goes from bare skin to a visible shadow in about a week. On a 5 cm scissor cut, one month adds about 20 percent to the length and mostly changes how the hair sits rather than how the cut reads.

This is the real reason short cuts need more frequent visits, which we map out in how often to get a haircut.

Why lineups fade faster than the rest of the cut

A lineup blurs within days because the razor takes the edge down to skin, so any growth at all breaks the line. The forehead, temples and neck are also where the eye goes first, which makes two or three millimetres look like more.

That is why the lineup, not the fade, is usually the first thing clients notice going soft. If you want to understand the edge itself, see our page on what a lineup is and on how long a lineup lasts.

Does hair grow faster in summer?

Some people swear their hair grows faster in the warm months, but any seasonal difference is small and not something you could plan a haircut around. What does change in an Ontario summer is humidity: hair swells, curls tighten and a two-week-old fade can look puffier than it really is.

In winter the opposite happens. Dry indoor heat and toques flatten hair against the head, so regrowth can look shorter than it is until you wash and style it.

When slow or patchy growth is worth a doctor's visit

If hair suddenly sheds in handfuls, comes out in round smooth patches, or stops growing back after a cut, that is a question for a family doctor or a dermatologist rather than a barber. The same goes for a scalp that is sore, scaly or bleeding. We will often spot changes at the back or crown that you cannot see yourself and mention them, but diagnosing the cause is a medical job.

Gradual thinning at the temples or crown is common and has its own styling approach; our guide to haircuts for a thinning crown covers the options.