Growing a millimetre at a time
Nails grow so slowly that you only notice when they need cutting. A fingernail adds about three and a half millimetres a month, roughly the thickness of a coin every two weeks, and toenails grow at less than half that speed. It does not sound like much, but nails never stop growing, and over a lifetime every clipped sliver adds up to a surprising length. The measuring tape above lines up each nail as if every clipped bit had stayed on, so you can see how far past a ruler, a metre stick or even a doorway they would reach.
Switch between fingernails and toenails to compare. The toenail figure is always shorter, because toes grow so much more slowly, which is also why a damaged toenail takes more than a year to replace.
How we calculate it
We use the growth rates measured in a 2010 study of healthy young adults: 3.47 mm a month for fingernails and 1.62 mm a month for toenails. We multiply those by the months you have been alive to get the length of one uncut nail. For the total, we add ten fingernails and ten toenails together. Children’s nails grow a little faster than adults’ and older people’s more slowly, so this is a middle estimate.
| Time | Fingernail | Toenail |
|---|---|---|
| One week | 0.8 mm | 0.4 mm |
| One month | 3.5 mm | 1.6 mm |
| One year | 4.2 cm | 1.9 cm |
| Ten years | 42 cm | 19 cm |
| Fifty years | 2.1 m | 97 cm |
Worked example. Someone who has lived 438 months has grown 438 × 3.47 mm = 1.52 metres on each fingernail and 438 × 1.62 mm = 0.71 metres on each toenail. All twenty nails together come to about 22.3 metres, roughly the length of a tennis court.
What your nails say
Because nails grow steadily, they keep a slow record of your health. A serious illness or a big shock can leave a faint ridge across every nail at the same point, called a Beau’s line, which then grows out over the following months. Doctors sometimes use the position of the line to estimate when the event happened.
Questions people ask
How fast do nails grow?
A 2010 study published in the Journal of the American Academy of Dermatology measured fingernails growing about 3.5 mm a month and toenails about 1.6 mm a month in healthy adults.
Do nails grow faster on some fingers?
Yes. Nails on your dominant hand and on longer fingers tend to grow a little faster, and the middle fingernail is often quickest. Nails also grow faster in summer and in younger people.
Do nails keep growing after death?
No. That is a myth. The skin dries and pulls back after death, which can make nails look longer, but they do not grow.
How long does it take to regrow a whole nail?
About four to six months for a fingernail and twelve to eighteen months for a big toenail.
Sources. Yaemsiri, Hou, Slining & He (2010), Journal of the American Academy of Dermatology, “Growth rate of human fingernails and toenails in healthy American young adults”. Calculations run in your browser; nothing you enter is sent anywhere.