What is the diameter of healthy hair? The average diameter of healthy hair is 40-120 microns (1 micron = millionth of a meter). DHI Mexico2018-02-14T23:42:22+00:00December 5th, 2017|DHI|0 Comments Share This Story, Choose Your Platform! FacebookTwitterRedditLinkedInWhatsAppTumblrPinterestVkXingEmail About the Author: DHI Mexico