Here are the reasons:
>>Some doctors believe that repetitive trauma to the fingernails causes them to regenerate, or grow, at an accelerated rate. This means that people who bite their nails are more likely to have nails that grow faster than people who don't bite their nails.
>>ALSO since we use our hands much more often and dexterously than our toes (i.e. picking up stuff, pushing buttons, etc.) that our fingers receive much more stimulation than our shoe-covered toes and therefore the fingernails grow, as a regenerative response to the trauma, much faster than the toenails.
>>Some people also note that the fingernails of their dominant hand (the one you write with, swing a bat with, etc.) also tend to grow slightly faster than the other hand.
>>The idea here is that the body's circulatory system is much better at pushing fresh, oxygenated blood to the hands and fingers than it is to the feet and toes. That's true - ask any diabetic who's got problems with numb toes and you'll learn: the heart favours the hands. Therefore, the increased blood-flow and oxygen level causes the fingernails to grow faster than the toenails
3. Toenails are thicker:
>>The thicker the nail, the longer it takes to grow.
4. The longer the finger (or digit), the longer the nail:
>>There's also some evidence that the nails on the longer fingers grow faster than the nails on the shorter fingers. However, this theory seems to be closely related to the idea that the nails on the fingers you use most often tend to grow the fastest. For example, considering the Trauma theory ), the longer fingers are more likely to hit things more often.