The 'U' in 22U stands for rack unit — a standardized vertical measurement used globally for mounting IT equipment in server racks and cabinets. 8 cm) of vertical rack-mount space. You'll get a precise, actionable answer to what 22U means for your IT infrastructure — including exact height (38. What Is a Rack Unit (U / RU)? Ready to Optimize Your Server Rack Setup? Rack Units, or “U,” are the standard. ✅ A 22U server rack is exactly 38. 75-inch rack units of equipment — and most common models are 600 mm deep × 600 mm wide, supporting 600–800 kg static load. 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. A rack unit (abbreviated U or RU) is a unit of measure defined as 13⁄4 inches (44.