General Considerations. Hair grows approximately ½ inch per month, for a total of six inches in one year. This rate is an average across races. Asian hair grows slightly faster than this average, Caucasian hair grows near the average,and black hair trends to grow at or just below this average each month.eneral Considerations. Hair grows approximately ½ inch per month, for a total of six inches in one year. This rate is an average across races. Asian hair grows slightly faster than this average, Caucasian hair grows near the average,and black hair trends to grow at or just below this average each month.