How long does it take for hair to grow? hair grows about half an inch (1.25 cm) per month, which means it takes about six months to grow out a pixie cut and up to two years to grow out very long hair. However, several factors can affect hair growth rates, including genetics, age, diet, stress, and hair care practices. To promote hair growth, it's essential to maintain a healthy diet, minimize stress, and avoid damaging hair care practices like heat styling and chemical treatments.