Nail clippers are one of those household tools nobody thinks about until they can't find them. Every week or two, out they come, and a few tiny crescents disappear into the trash. It never seems like much. But your nails never take a break, so where does all that growth add up to?
Here's the short answer: on average, human fingernails grow about 3.5 millimeters a month. Over a full year, that comes to roughly 42 millimeters, or a little more than an inch and a half. Toenails are much slower, growing only about half that fast.
Why Some Nails Grow Faster
Not every nail keeps the same pace. In mammals, nail growth is linked to the length of the bone at the very tip of the finger. That's why the nail on your index finger grows faster than the one on your little finger.
Fingernails can grow up to four times faster than toenails. A fingernail takes about three to six months to replace itself completely, while a toenail needs 12 to 18 months. If you've ever lost a toenail, that explains the long wait.
Your personal speed depends on many things. Age, sex, the season, how active you are, what you eat, and the genes you inherited all play a part. So your yearly total may run a little ahead of or behind the average.
What a Nail Is Made Of
Fingernails are made of a tough protein called alpha-keratin. It's the same basic material found in the claws, hooves, and horns of other animals with backbones. In fact, our nails and the hooves of running mammals both evolved from the claws of earlier creatures.
The part you clip is made of layers of dead, compacted cells, which is why trimming doesn't hurt. The only living, growing part sits under the skin at the base of the nail. The pale half-moon you can often see near the base, especially on your thumb, is called the lunula, Latin for "small moon."
A Myth and Some Record Breakers
You may have heard that nails keep growing after death. That's a myth. After death, the skin dries out and pulls back, which only makes the nails and hair look longer.
Some people have let their nails grow for decades. Shridhar Chillal of India stopped cutting his nails in 1952. He went on to set the record for the longest fingernails ever on a single hand, with a combined length of about 358 inches. His thumbnail alone measured nearly 78 inches. In 2018, the nails were finally cut with a power tool at the Ripley's Believe It or Not! museum in New York City.
Little Windows on Your Health
Because nails grow slowly and steadily, they keep a kind of record. Changes in color, thickness, or shape can sometimes hint at problems elsewhere in the body, and doctors have looked at nails for clues since ancient times. Deep grooves across the nail, called Beau's lines, are usually just a natural part of aging. If you notice a change that worries you, talk to your doctor.
So the next time you reach for the clippers, give your nails a little credit. They've quietly been adding a little under a millimeter every week, and over a year that's more than an inch and a half of steady, patient work.
