Unless you’re a nail biter (in which case your nails will never grow) or a werewolf (in which case they’ll grow in seconds), this info should answer your question:
The overall growth of the nail within one month is approximately 3mm. However this does vary from person to person. To completely out grow a nail can take up to 6 months. As mentioned, growth rate does vary from person to person, there are many contributing factors such as; weather, health, age and a well balanced diet. The nail tends to grow faster in our early years, reaching its peak around the age of 10–14 and then the nail growth gradually slows down, as we get older. Growth is accelerated in the summer, during pregnancy and during sleep. Poor blood circulation, malnutrition, certain illnesses and some medications can slow down the growth rate. Each nail grows at a different rate. The smallest nail that we often refer to as our “pinkie” is the in fact the slowest, then the thumbs. The index finger generally grows at an accelerated rate in comparison to the others.
Chew on that…