How fast do fingernails grow?

Nails are made of keratin, the same tough protein found in hair, and grow from a hidden area under the skin called the matrix. A 2010 study measured average fingernail growth at about 3.47 millimetres per month, so a whole fingernail takes around six months to replace. A toenail can take 12 to 18 months. Nails grow faster on your dominant hand, on longer fingers such as the middle finger, in summer and when you are young. Illness, poor diet and some medicines can slow growth and leave visible ridges.