Researched and written by Curl Centric. Read by an AI voice.
Half an inch a month is one of two answers from the same study. We walk you through both numbers, whose hair each one came from, and what they mean for your length.
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The full guide, with every source: How long it takes for hair to grow.
Transcript
This is Curl Science by Curl Centric.
Free 50-page guide
Your hair is already growing. The problem is keeping it.
On average, hair grows a third to half an inch a month, and curlier hair tends to grow more slowly. If your length looks stuck, that’s your hair breaking off as fast as it grows in. Here are the seven causes of breakage and the weekly routine that stops them.
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There are two hair growth rates in the study everyone quotes. Almost nobody hears about the second one.
Here's what happened. In 2001, researchers publishing in the British Journal of Dermatology measured hair growth across different groups of volunteers, using the same method on all of them. Caucasian hair grew about 396 micrometers a day, which works out to roughly half an inch a month. African hair grew about 256 micrometers a day, which is closer to a third of an inch. Same study, same method, two numbers, and only the first one ever made it into circulation.
So half an inch a month isn't wrong. It's just one of the answers.
Which means the useful question isn't how fast hair grows. It's which number is closer to yours, and how much room there is on either side of it.
There's a lot of room. Inside a single group, the slowest grower came in at 150 micrometers a day and the fastest at 363. That's nearly two and a half times the difference between two people with the same hair type. It was also a small study, thirty-eight people, so treat these as rough anchors rather than promises. Wherever you sit, you don't get to know your exact rate, and nobody selling you anything knows it either.
Now here's the part that changes what you do on wash day, and this part is the same for everybody.
Take whichever number is closer to your hair. Over a year, that's somewhere between about three and a half and five and a half inches of brand new hair. It arrived at your scalp on schedule. The question is whether it was still there at the ends in December.
Because that's where length actually goes missing. Hair doesn't stop growing when it stops getting longer. It stops getting longer when the ends start breaking off as fast as the roots push new hair out.
That has been measured too. In 2007, researchers examined the hair of 1,042 South African schoolchildren and found that combed hair reached a length and then simply stayed there, usually within about a year of a haircut. Not because the follicle quit. Because breakage had caught up with growth.
The plateau length in that study was around two inches, and that number is specific to the hair they measured. The mechanism isn't. Whatever your texture, a length plateau is not a ceiling your hair can't pass. It's a tie.
And a tie is good news, because a tie can be broken from either side. You can't do much about the growth side; that rate is mostly yours and you're stuck with it. The breakage side is almost entirely in your hands.
So here's where the leverage is.
Detangle on wet, conditioned hair, and start at your ends. Conditioner gives the comb something to slide on, so it passes through instead of snagging. Work up an inch at a time. It's slower than raking straight through from the roots, and every tangle you force apart is a strand you don't keep.
Watch the tension in your styles. The American Academy of Dermatology puts the ceiling on braids at six to eight weeks, and says plainly that if a style feels painful, it's too tight. Thicker braids pull less than fine ones. Shorter lengths are lighter, so they drag less. And your hairline should be the loosest part of any style, because it's the first place tension shows.
Protect your ends at night. They're the oldest hair on your head, they've been through every wash day you've ever had, and they break first.
None of that makes your hair grow faster. That's the point. You already have the growth. The only question is how much of it you're still holding at the end of the year.
We've put the full breakdown, with both studies and the numbers behind them, in a free fifty page guide. It's at curlcentric.com/keep-the-length.
That's it for this episode. If it helped, follow Curl Science in your podcast app so the next one reaches you, and leave us a rating while you're there. Curl Science is researched and written by the Curl Centric team, and it's read by an AI voice.
