Fingernail growth averages out to about a tenth of a millimeter a day.
Toenails are about a half to a third slower, and drugs or disease can change the growth rate.
There are differences from finger to finger.
The middle and fourth finger tend to grow a little faster than the fifth and the thumb.
Nails grow faster in summer, some research indicates, while winter and a cold environment tend to slow nail growth.
Other studies seem to find that the right-hand fingers grow faster than the left, which might be tied to handedness, and that stimulation, such as massage, helps them grow faster.
People with the neurotic habit of rubbing a digit would find that the nail they rubbed grew faster.
Contrary to childhood myth, nails do not continue to grow after death.
That is an optical illusion.
Tissues around the nail tend to shrink away from the hard nail after death, giving the impression of something still growing.