On average, hair grows ½ inch per month and 6 inches per year. Normally men’s hair grows at a slightly faster rate than women’s at 6-7 inches per year.Hair grows faster in the summer than in the winter because hair growth requires a warm temperature. No other mumbo jumbo methods can improve hair growth.n average, hair grows ½ inch per month and 6 inches per year. Normally men’s hair grows at a slightly faster rate than women’s at 6-7 inches per year.