However, the most common server rack size you'll encounter in data centers is 42U. A rack unit (abbreviated as U, less often as RU) is a standardized unit of measurement used to describe the height of equipment designed to be mounted in a 19 or 23-inch-wide server rack. With this reality in mind, keep reading for a guide to server rack sizes, including why server. Common server rack sizes are 19‑inch width, heights like 42U or 48U, and depths from ~24″ to 48″. Choose size based on equipment type, cooling, space, and future growth. Most IT environments default to 42U, 19-inch width, and 1000–1200 mm depth unless space constraints or special equipment dictate. One rack unit equals 1. 5 inches tall, a 4U device is 7 inches tall, and so on. A 42RU rack will hold 42 1RU units or 21 2RU units.
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