It takes approximately six months for an entire fingernail to grow back after falling off or being pulled from the root, says Kids Health. It takes so long for a nail to grow back after a traumatic event because nails grow slowly.
Fingernails grow at a rate of approximately one-tenth of an inch per month, according to Kids Health. Fingernails begin growing at the base of the nail or nail root, which is located just under the cuticle. Protein or keratin cells build up in this area, forming a hard plate. As the plate gets pushed forward by the accumulation of new cells, nail growth occurs.