The proper height to install outdoor wall mounts - The height of an outdoor wall mount should be based on the height of the door. For example if a lantern is only used on one side, it should be approximately one-third the height of the door. When two lanterns are used on either side of the door, they should each be approximately one-fourth the height of the door. In either case, if you choose a fixture with a long tail or top scroll, be cautious of the overall bulk of the fixture as the height should approximate one-half the visual height of the door. The lanterns should be mounted so the filament of the bulb is approximately 66” above the threshold of the door. Depending on the outlet box location, different mounting arms (on the top or bottom) can be selected to place the filament correctly. Don’t undersized your lanterns – As a rule of thumb, lanterns will appear about half the size from 50 feet away. Visualize the front of your home as guests and neighbors would view it from the street, and when in doubt, always go larger.
Source: Hinkley Lighting