Question: what are the dimensions of a standard size mailbox?
Answer: 1: Approximately 19 inches long by 6 ½ inches wide by 8 ½ inches high; No. 2: Approximately 23 ½ inches long by 11 ½ inches wide by 13 ½ inches high. 1954: The Department approved a third, medium size of the standard, tunnel-shaped rural mailbox: No.