The answer to this question is actually a bit complex. The rate of growth of human fingernails varies, depending on the person, the nail in question, and the time of year. As a general rule, human fingernails grow between 0.5 inches (1 cm) and 4 inches (10 cm) per year, and a number of things can influence this growth rate. Incidentally, fingernails grow approximately five times as fast as toenails, for those who are curious.
Among the many factors which influences the rate of growth is age. Younger people tend to grow their fingernails more quickly, especially if they eat healthy, varied diets. To improve the strength and appearance of fingernails, people can consume gelatin, which will help build thicker, stronger nails. Gelatin can also contribute to hair health, as well, although it will not significantly impact the rate of growth for human hair. Dietary imbalances can cause spotting or ridges on the nails, and an overload of certain toxins can also have an impact on nail growth and appearance.
One must also consider the finger when looking at the rate of nail growth. Longer fingers appear to grow nail material more quickly, as do the fingers on the dominant hand. On most people, the middle finger of the dominant hand grows a nail most quickly, while the thumb or pinky of the other hand has the slowest rate of nail growth.
Human fingernails appear to grow more quickly during the daylight, which means that they also grow more during the summer, when daylight hours are increased. As human fingernails grow, they can be shaped with trimming, a technique which can also be used to strengthen the edge of the nail by trimming away thin, ragged material on the nail and cuticle. Some people also like to oil their nails to keep them fully hydrated, or to use nail-strengthening solutions if they have especially thin or pitted nails.
Contrary to popular belief, human fingernails do not continue to grow after death. The illusion of growing fingernails is created by the dehydration which the human body experiences after death. As the body dehydrates, soft tissue starts to shrink and pull away, which can make it look as though the hair and fingernails have grown. The shrinking tissue can also expose the teeth, which explains why the dead appear to be grinning.
