This is a question I hear a lot!
Knowing how often you should get a haircut has a lot to do with you hair goals and the chemical processes you put your hair through on a regular basis.
It's important to know that, on average, hair grows about a 1/2 an inch a month.
If you are keeping-up on a short hairstyle you will probably need to reshape your style every 4 to 8 weeks. Short hair styles appear to grow out quickly because most short hair styles have blunt lines.
Medium Length Hair:
If you like the length of your hair, I would suggest a haircut every 6 to 8 weeks to keep your hair looking healthy. If you are growing your hair out, opt for a trim every 8 to 12 weeks.
If your hair is long and you want to keep it long, it is very important to get regular haircuts to keep your long hair looking healthy! Long hair is very OLD. Like anything that ages, the older your hair gets, the more fragile it is. Long hair is more susceptible to having split ends and breakage, ESPECIALLY if you color and/or highlight your hair. Regular trims will help keep your hair healthy and strong. I would suggest a trim about every 6 to 12 weeks, or no longer than 4 months between haircuts to keep your hair looking and feeling healthy.
Colored or Chemically Treated Hair:
If you color your hair (any color, lighter or darker) or perm your hair regularly (about every 6-12 weeks) you may needs trims more frequently. The reason? Because chemical processes can contribute to split ends, breakage, and dryness. More frequent hair cuts may help prevent these things by removing the dry ends.
Growing Your Hair??:
Regular (depending on the length of your hair) haircuts will minimize breakage and maximize your hairs' growth potential!