There are 3 phases of growth for scalp hair. The time these phases last varies from person to person.
Anagen Phase, or growth phase, is when all new hair growth occurs. During this phase hair grows at its normal rate (an average of one-half inch per month), and 90% of the hairs on your head will be in the anagen phase at any given time. Each specific hair can be in the anagen phase for an average of 3-5 years.
Catagen Phase, 2–3 weeks. The catagen phase is a short transition stage that occurs at the end of the anagen phase. It signals the end of the active growth of a hair. The hair follicle contracts and detaches from the dermal papilla (where it gets its nutrients). The hair bulb disappears and the root end of the hair forms a rounded club. Less than 1% of the hair will be in the catagen phase at any given time.
Telogen Phase, around 3-6 months. The telogen phase is the resting phase of the hair follicle. At any given time, 10%-15% of all hairs are in the telogen phase. This phase lasts for about 100 days. During this phase the hair follicle is completely at rest. This phase lasts until the fully grown hair is shed or after the start of the next anagen phase when it gets pushed out of the follicle. About 25-100 telogen hairs are shed normally each day.
Once the telogen phase ends, the anagen phase of that follicle begins again. The whole cycle repeats on an average of every 4-5 years.
Some people will say that if you’ve been trying to grow your hair for over 5 years, you may have to come to terms with the fact that your hair won’t grow as long as you hoped. This may be true for a rare few, but I really believe that anyone can grow long hair, but I do think that certain people can’t appreciate the growth because of their styling techniques and trimming too often. If you’re trying to grow your hair out quicker, my advice is to stop trimming and start taking care of your ends in order to appreciate/retain all of your growth. I was a victim of the idea that I had to trim my ends every 6-8 weeks. Well, guess what? I was trimming off new length. I was so brainwashed that I had to do this for my hair to grow. I was growing my hair out for several years and still no progress because all this length was scattered about on my stylist’s floor. It’s been well over a year since I had a professional trim and I have retained over 6″, the average. This is not my first time going over a year without a trim, but I do think a year is my threshold. I’m probably going to trim off 1/2″ sometime in the next few weeks just to shape up my hair. I ‘search and destroy’ bad ends as often as necessary and I could probably go much longer without a full trim, it’s just a personal preference. If your ends are messed up and you use heat a lot, I suggest getting a good professional trim. It will be like starting from scratch, but hopefully this time around you treat your hair better.