Fingernails grow about 3.47 millimeters per month, or roughly a tenth of a millimeter per day. That’s slow enough that you won’t notice daily changes, but fast enough that most people need to trim their nails every week or two. Toenails are considerably slower, growing at about 1.62 millimeters per month, less than half the speed of fingernails.
Fingernails vs. Toenails
The difference in speed between fingernails and toenails is striking. At 3.47 mm per month, a fingernail takes about 4 to 6 months to completely replace itself from base to tip. A toenail, growing at just 1.62 mm per month, can take up to 18 months for a full replacement. That’s why a damaged toenail feels like it takes forever to grow out, and why toenail fungus is so stubborn to treat.
Not all fingernails grow at the same pace either. Your middle finger nail typically grows the fastest, while your thumbnail and pinky nail tend to be the slowest. Nails on your dominant hand also grow slightly faster than those on your non-dominant hand, likely because that hand gets more blood flow from regular use.
What Makes Nails Grow
All nail growth starts in a small pocket of tissue called the nail matrix, tucked just beneath the skin behind your cuticle. The matrix is a factory of specialized cells that constantly produce new layers of hardened protein. About 90% of your nail comes from the main part of this matrix, while the remaining 10% comes from tissue underneath the nail plate that also helps keep the nail attached to the skin below it. Each nail is built from 196 layers of cells stacked together.
Unlike hair follicles, which cycle between growth and rest phases, your nail matrix produces cells continuously. There’s no “off” period. This is why nails keep growing even when you’re sick, stressed, or not eating well, though the rate may slow down under those conditions.
How Age Affects Growth
Nail growth peaks in early adulthood and then gradually declines. After age 25, the rate slows by roughly 0.5% per year. That sounds minor, but it compounds over decades. By the end of an average lifespan, nail growth has dropped by about 50% compared to its peak. This is one reason older adults may notice their nails seem thinner, more brittle, or harder to maintain.
Harvard geneticist David Sinclair has suggested that nail growth rate can serve as a rough personal marker of biological aging. Faster growth reflects higher metabolic activity and good circulation. Noticeably slow or brittle nails, on the other hand, can sometimes signal underlying issues like poor vascular health, iron deficiency, or thyroid problems.
Other Factors That Speed Up or Slow Down Growth
Several things influence how quickly your nails grow beyond just age:
- Hormones: Pregnancy and other hormonal shifts often accelerate nail growth due to increased metabolic activity. Thyroid disorders, particularly an underactive thyroid, can slow it down noticeably.
- Nutrition: Iron, zinc, and B vitamins all play a role in healthy nail production. Deficiencies in these nutrients can lead to slower growth, brittleness, or visible changes like ridges and discoloration.
- Circulation: Better blood flow to your fingertips means more nutrients reaching the nail matrix. This is likely why your dominant hand’s nails grow a bit faster, and why people with circulatory problems often have slower nail growth.
- Season: The data here is mixed. A classic 35-year self-study by American doctor William Bennett Bean concluded that climate and season have no meaningful effect on growth rate. Other studies have found a slight increase during summer months, possibly tied to increased blood supply to the fingertips. If your nails seem to grow faster on vacation, the more likely explanation is that you’re simply using your hands less, so nails aren’t being worn down as quickly.
What to Expect After Losing a Nail
If you lose a fingernail completely, whether from injury, infection, or a medical procedure, expect 4 to 6 months for a full regrowth. The new nail may look slightly different at first, with ridges or uneven texture, but it typically smooths out as it matures. Toenails are a longer commitment. A fully lost toenail takes up to 18 months to grow back entirely, and it’s common for the new nail to appear thicker or slightly discolored for a while.
During regrowth, the nail matrix is doing the same thing it always does: producing new cell layers continuously. The process can’t be meaningfully sped up with supplements or topical treatments, though keeping the nail bed clean and protected helps ensure the new nail grows in healthy. Patience is the main requirement.