The fingernails and toenails are hardened, protective structures made from keratin, a protein also found in hair and the outer layer of skin. Nail growth originates from the nail matrix, a specialized area of tissue located just beneath the cuticle at the base of the nail bed. New cells are constantly produced in this matrix, pushing the older, dead cells forward to form the visible nail plate.
Calculating the Weekly Growth Rate
The average rate of human fingernail growth is approximately 3.47 millimeters per month, which is about one-tenth of a millimeter each day. Translating this monthly average into a weekly measurement, a healthy fingernail will grow between 0.7 to 0.9 millimeters in a single week.
The precise length of the nail plate is determined by the size and activity of the matrix, which is metabolically active and continuously producing new cells. The new nail material moves forward over the nail bed, which is why growth is measured in linear distance. The standard rate of growth for a normal fingernail is generally considered to fall within the range of 0.5 to 1.2 millimeters per week.
Biological Factors Influencing Speed
The weekly growth rate is not fixed for every person, as several internal biological factors cause it to deviate from the average. Age is a significant determinant, with nail growth typically peaking in younger individuals and gradually slowing down as a person gets older due to the general slowing of metabolic processes.
Circulation plays a large part in the speed of nail growth because the matrix requires a steady supply of nutrients and oxygen delivered by the blood. Increased activity or minor trauma, such as frequently using the dominant hand, can stimulate blood flow and slightly increase the rate of cell production. Hormonal changes, such as those experienced during pregnancy, can also temporarily accelerate growth.
The overall health and nutritional status of the body provide the necessary building blocks for new nail cells. Deficiencies in vitamins like Biotin (B7), or minerals such as zinc and iron, can slow the rate of growth and lead to weaker nails. Fingernails also grow slightly faster during warmer periods, suggesting a seasonal variation linked to temperature and increased peripheral blood flow.
Fingernails Versus Toenails
Toenails grow substantially slower than fingernails, averaging only about 1.62 millimeters per month. This means toenails grow at roughly half the speed of fingernails.
One primary theory explaining this difference involves the level of physical activity and resulting minor trauma. Fingernails are constantly exposed to friction and minor impacts from daily tasks, which stimulates blood flow and encourages quicker growth. Toenails, by contrast, are often protected inside shoes and experience less stimulating activity.
Another contributing factor is the distance from the heart, which impacts blood circulation. Because the feet are further from the heart than the hands, they receive less robust blood flow. This limits the rate at which nutrients reach the nail matrix in the toes. As a result, a lost toenail can take between 12 to 18 months to fully regrow, compared to the three to six months required for a fingernail.