You cut them, they come back. But how fast, exactly? A careful study of healthy young adults measured it, and the gap between fingers and toes is bigger than most people think.
The numbers
In a 2010 study published in the Journal of the European Academy of Dermatology and Venereology, researchers asked young American adults to mark their nails and measure how far the mark moved over one to three months.
The result: fingernails grew an average of 3.47 mm per month, a little over a tenth of a millimetre per day. Toenails grew just 1.62 mm per month, less than half as fast.
Not all fingers are equal
Left and right hands grew at about the same speed. But the little fingernail grew more slowly than the other fingernails, and the big toenail grew faster than the other toenails.
Younger age, being male and nail biting all seemed linked to slightly faster growth, but those differences were not strong enough to be certain.
Faster than in the past?
The researchers noted that nail growth in their study was faster than in estimates made decades earlier. The reason is not known.
What it means in real life
At about 3.5 mm a month, a fingernail that is completely lost takes several months to grow back. A lost big toenail can take a year or more, which is why a bruise under a toenail seems to stay for so long.
Nails are made of keratin, the same tough protein found in hair. They grow from a hidden area under the skin at the base of the nail, called the matrix. Creams on the nail itself cannot speed that up.
In short
- Fingernails grow about 3.47 mm per month on average.
- Toenails grow about 1.62 mm per month, less than half as fast.
- The little fingernail is the slowest; the big toenail is the fastest toenail.
Sources
- Yaemsiri et al. (2010), Growth rate of human fingernails and toenails in healthy American young adults (PubMed)
- Harvard BioNumbers: Average fingernail and toenail growth rate
This article is for curiosity and learning only and is not medical advice.