A height of 4 1/2-feet is optimal and the most ergonomic height for accessing the upper cabinets for anyone over 4-feet tall. Shorter people might need a step stool to reach the upper portion of the cabinet. Standard upper cabinets are 30-inches tall making the entirety of the cabinet easily accessible for 5-feet 8-inch tall people without a step stool. Cabinet space over 30-inches tall are not readily accessible except for NBA players.
Upper cabinets are typically 12-inches deep. Anything deeper that that makes accessing the rear of the upper shelves more difficult.