Rack Units (RU): Sizes, Standards & Uses 2026
So when you mount a 1U device, it lines up with a three-hole pattern spaced to fit its height perfectly. If you''re working with a standard 4-post or 2-post
Contact UsStandard mounting holes for a 1U chassis
Home / Standard mounting holes for a 1U chassis
A typical full-size rack is 42U, which means it holds just over 6 feet (180 cm) of equipment, and a typical "half-height" rack is 18U–22U, which is around 3 feet (91 cm) high. The mounting-hole distance (as shown to the right) differs for 19-inch racks and 23-inch racks: 19-inch racks use uneven spacings (as shown to the right) while 23-inch. Originally defined by the EIA-310 standard, the rack specifies a front panel width of 19 inches (482. 26 cm), mounting hole spacing, and critical clearance allowances — plus actionable guidance on verifying physical fit, avoiding common installation errors, and selecting. 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.
