LCHACHILA where should a mezuzah be placed? Assuming 80 inch door post. Upper 1/3 begins at 53 1/3 inches from the bottom (80/3 =26.67. 80-26.67=53.3). Should the MEZUZAH be placed at right above 53 inches exactly? It seems too low. Or l’chatchilla can it be placed between a TEFACH from the top (4inches CHAZON ISH) and 53 inches from the bottom. Anywhere in between as long as its the upper 1/3 and a 4inches from the TOP? LECHATCHILLA
The best place to put the mezuza is right after the beginning of the top third of the doorway. Although it is still kosher if it is higher, until a tefach before the top of the doorpost, the best place to place it, is as stated.
Rambam brought in Bais Yosef and Shulchan Aruch Y:D 289-2, It is also the preferred place for kabalistic reasons, see Birkei Yosef Y:D 298-3.