Dermatologists confirm that the rate of fingernail growth outstrips that of toenails, with the former lengthening anywhere from slightly faster to perhaps three times as fast. The American Academy of Dermatology puts the average rate of fingernail growth at about 0.1mm a day.
The reason for the difference is uncertain but speculation is it is because of blood circulation which is better in the hands than in the feet. According to biopsy reports, the further down in the leg, the slower things are to heal, with an even slower cell turnover rate as you go further down to the toes.
Fingernail cells are formed in the matrix, under the cuticle, and are gradually extruded, dying, hardening and becoming mashed together as they are pushed out by the new cells. The root of the fingernail produces most of the volume of the nail and the nail bed beneath it. The bed contains the blood vessels, nerves and melanocyte cells responsible for skin colour. As the nail is produced by the root, it streams down along the nail bed, making it thicker. Nail growth is also affected by hormones, age, climate and time of year. Hair seems to grow a little faster in summer and the same is true for nails.