These are the standard rectangular boxes you often see used for single light switches or electrical outlets in US homes. Their dimensions are generally around 2 inches wide by 4 inches tall, with depths varying from 1-1/2 inches to 3-1/2 inches. What are standard electrical box dimensions? Standard sizes vary by type, but single-gang boxes are typically around 2″ × 3″ × 3. Typically available in depths ranging from 1-1/2 inches to 2-1/8 inches, their square shape provides ample internal volume for making multiple wire connections and. Within electrical installations regulated by NEC and UL standards, the terminology surrounding junction boxes extends well beyond simple measurements of length and width. Choosing the proper enclosure requires fluency in the language of gangs, physical footprint, and—most importantly— internal. The measurements of a standard single-gang device electrical box are typically 2 ¼ inches wide, 3 ¾ inches high, and 2 ½ to 3 ½ inches deep. Selecting the correct size is not just about fit; it is a critical safety requirement governed by the National Electrical Code (NEC) to. Choosing the correct electrical box size is essential for safety, compliance, and proper installation.