A 1U server rack measures exactly 1. 45 mm) in height and fits standard 19-inch racks. 6 mm), allowing different hardware from various manufacturers to fit in the same enclosure. This compatibility has made rackmount systems the backbone of data centers, telecommunications rooms. For example, a typical full-size rack cage is 42U high, while equipment is typically 1U, 2U, 3U, or 4U high. The Eurocard specifies a standard rack unit as the unit of height; it also defines a similar unit. U (rack unit, RU) is a unit of equipment height in a 19" rack. Important: U describes height only, but a server's real "capabilities" are also determined by chassis depth, internal layout, airflow, rails, power, and expansion (PCIe/risers, NVMe. Convert inches, cm, or mm to rack units and rack units back to height in inches, cm, and mm for standard server racks with exact 1U conversions. The calculator uses two formulas depending on the direction of conversion.