Quick Answer: Fingernails grow roughly 3 to 3.5mm per month on average, and that rate rises measurably in warmer months - likely from increased circulation to the extremities and greater use of the hands. Growth is also faster on your dominant hand, faster on the middle finger than the little finger, faster in younger people, and slower during illness. Toenails grow at roughly a third to a half the fingernail rate.

If your nails suddenly slowed, look at circulation, illness, and nutrition - not polish.

Why does season change the rate?

Circulation, mostly, plus how much you use your hands.

Nails are produced by the matrix, the tissue under the base of the nail where new cells are generated, keratinize, and are pushed forward. The matrix is metabolically active and depends entirely on blood supply, so anything that changes circulation to the fingertips changes production rate.

In warm weather, peripheral blood vessels dilate to shed heat, which increases blood flow to the hands and feet. In cold weather they constrict to conserve core temperature, reducing it. The seasonal difference in nail growth is consistently observed and this is the most plausible mechanism.

There is likely a second contributor. Minor repeated trauma to the nail appears to stimulate growth - which is why the dominant hand grows faster, and why the middle finger, being longest and most exposed to knocks, grows fastest of the five. In summer, hands are used more and protected less, which fits the same pattern.

Typical rates, for reference:

• Fingernails: roughly 3 to 3.5mm per month, so a full fingernail replaces itself in about four to six months
• Toenails: roughly 1 to 1.5mm per month, taking twelve to eighteen months for full replacement
• Middle finger fastest, thumb and little finger slowest
• Dominant hand faster than the non-dominant

The toenail figure explains a lot of frustration. A damaged toenail takes over a year to grow out fully, which is why toenail issues seem to last forever - they genuinely do.

What else speeds nails up or slows them down?

A longer list than most people expect, and most of it is not under your control.

Speeds growth up:

• Youth. Growth peaks in the teens and twenties and declines gradually thereafter. The decline from young adulthood to older age is substantial - roughly a third or more.
• Pregnancy. Frequently reported and likely hormonal plus increased circulation.
• Minor repeated trauma. Typing, manual work, and general hand use.
• Warm weather and warm environments generally.
• Some medications, including certain thyroid treatments.

Slows growth down:

• Illness, particularly with fever. The body deprioritizes nail production, and a severe illness can leave a visible horizontal groove - a Beau’s line - marking the point at which growth paused. Because growth rate is known, the position of the line dates the illness fairly accurately, which is a genuinely useful diagnostic detail.
• Poor circulation, from cold, from smoking, or from vascular conditions. Raynaud’s phenomenon in particular produces episodic constriction and slower, more brittle nails.
• Nutritional deficiency - iron, protein, biotin, and zinc among the relevant ones. Deficiency slows growth; supplementation above sufficiency does not speed it up. That distinction is the whole story on nail supplements.
• Age, steadily.
• Certain medications, notably chemotherapy agents, which frequently produce visible growth-arrest lines.
• Hypothyroidism, which slows nail growth alongside other systemic effects.
• Immobilization. A limb in a cast grows nails more slowly, which supports the circulation-and-use explanation.

What does not meaningfully change growth rate: nail polish, gel manicures, cuticle oil, base coats, and nail hardeners. These affect nail quality, appearance, and breakage - which changes how long your nails get - but not the rate of production at the matrix. The distinction matters, because most products marketed for growth are actually reducing breakage, and it is worth knowing which problem you are solving.

What can you actually influence?

Two things: the underlying inputs, and breakage. Only one of those is about growth.

Inputs, which matter only if something is deficient:

• Adequate protein. Nails are keratin, a protein. Genuinely low intake shows up in nail quality within months.
• Iron. Deficiency is common, particularly in menstruating women, and produces brittle, sometimes spoon-shaped nails. Worth testing rather than guessing, since iron supplementation without deficiency carries its own risks.
• Biotin. The evidence is limited and applies mainly to people with brittle nail syndrome, where some studies show improvement at around 2.5mg daily over several months. In people without a deficiency, evidence for benefit is weak, and biotin interferes with several common lab tests including thyroid and cardiac markers - tell your doctor if you take it.
• Circulation. Keeping hands warm in cold weather, and not smoking, both plausibly help. Smoking cessation improves peripheral circulation measurably.

Reducing breakage, which is what actually determines nail length:

• Keep them shorter through a growth-out phase. Longer nails have more leverage and break more.
• Moisturize the nail and cuticle, especially at night. Hydrated keratin is more flexible and less prone to snapping.
• Wear gloves for washing up and cleaning. Repeated wet-dry cycling and detergent are among the biggest causes of splitting.
• File in one direction with a fine grit. Coarse files and sawing back and forth cause micro-tears at the free edge that propagate into splits.
• Take breaks from gel and acrylic, and have them removed properly rather than picked off. Peeling off gel takes nail plate layers with it.

When to see a doctor rather than change products: sudden slowing or thickening, colour changes, pitting, spooning, separation from the nail bed, or dark streaks. A new dark line running the length of a single nail should always be assessed. This is general information, not medical advice, and nail changes can reflect systemic conditions worth investigating.

What Nobody Tells You About Nail Growth

Your nails record the last few months. Because growth is steady and slow, a fingernail is a timeline of roughly four to six months. Ridges, grooves, and discolouration can often be dated by where they sit.

Nails do not keep growing after death. The tissue around them dehydrates and retracts, which exposes more nail. A persistent myth with a mundane explanation.

Everyone has vertical ridges eventually. They become more prominent with age and are the nail equivalent of fine lines - normal, not a deficiency. Horizontal ridges are the ones worth paying attention to.

Toenail issues take a year to grow out. Nothing accelerates it meaningfully. Knowing the timeline prevents a lot of pointless product-switching.

Nail growth supplements mostly work by reducing breakage. If a product made your nails longer, it very likely made them less fragile rather than faster-growing - which is a real benefit, just not the advertised mechanism.

Cold hands are a real factor. If you work in a cold environment or run cold, that plausibly contributes to slower growth and more brittleness, and keeping your hands warm is free.

The matrix is what matters, and it is under the skin. Damage to the visible nail grows out. Damage to the matrix - a crushing injury, aggressive cuticle work, repeated trauma - can permanently change how the nail grows. That is the argument for leaving cuticles alone rather than cutting them.

FAQ: Nail Growth Questions, Answered

How fast do nails actually grow?

Roughly 3 to 3.5mm per month for fingernails, and 1 to 1.5mm for toenails. Full fingernail replacement takes four to six months; toenails take a year or more.

Does biotin work?

There is some evidence in people with brittle nail syndrome at around 2.5mg daily over several months. Evidence in people without a deficiency is weak, and biotin interferes with several lab tests.

Why is one nail growing slower than the others?

Past trauma to that matrix, a localized infection, or reduced circulation to that finger. If it persists and is accompanied by shape or colour change, get it looked at.

Does polish stop nails from growing?

No. Polish sits on the plate; growth happens at the matrix under the skin. Polish can affect hydration and breakage, which changes achievable length.

Do nails grow faster after being cut?

No - that is a perception effect from the contrast with the shorter length. The rate at the matrix is unchanged.

TL;DR:

• Fingernails grow roughly 3 to 3.5mm a month, faster in warm weather because of increased peripheral circulation.
• Dominant hand and middle finger grow fastest; toenails grow at a third to a half the rate.
• Illness, poor circulation, age, hypothyroidism, and nutritional deficiency all slow growth measurably.
• Polish, gel, and oils do not change growth rate. They change breakage, which is what actually determines length.
• Sudden slowing, colour change, spooning, or a dark streak in one nail should be assessed by a doctor.

If you want longer nails, solve breakage. The growth rate is largely out of your hands.