Final answer:
Most exterior doors are standardized at 6 feet 8 inches high in the United States, equivalent to 80 inches, to accommodate average heights and ensure comfortable passage.
Step-by-step explanation:
Most exterior doors are 6 feet 8 inches high. This has become somewhat of a standard height in the United States for residential exterior doors
The dimension is derived from a common construction standard where door heights have been established to accommodate the average person's height and to provide a comfortable passage. Entry doors come in a variety of widths, commonly starting at 30 inches, but the height is usually consistent at 80 inches, which is equivalent to 6 feet 8 inches.