The most popular modern server rack and cabinet dimensions are 24 inches (600mm) wide, 42 inches (1066. Those dimensions support most IT equipment and typically handle power loads of about 8kW per rack or less. Rack Units Explained: The Foundation of Server Rack Sizes The fundamental measurement of rack height is. Common server rack sizes are 19‑inch width, heights like 42U or 48U, and depths from ~24″ to 48″. This follows the EIA-310 standard, which defines the mounting space between the vertical rails. Nearly all rack-mounted equipment—servers, switches, patch panels—is built to fit this standard 19” width. In real deployments, however, rack size is rarely just a measurement problem.