From Smaller Offices to Large-Scale Data Centers: Size Guide for Server Racks

Server racks may not be the most glamorous or exciting part of building a server network, but they are an essential piece of equipment that shapes your network. Ample rack space ensures you have enough room for all the hardware and cabling needed to run your network effectively. 

But that does not mean the biggest rack server rack is the best for any situation. Server rack sizes vary, and smaller racks can help maximize your network layout in tight spaces. Every space is different, so deciding on the best layout begins with understanding the different server rack sizes available.

Server Rack Sizes to Know

Server rack dimensions are measured in rack units, abbreviated as “U”. One rack unit is equal to 1.75 inches, or 44.45 millimeters, with a width of either 19 or 23 inches. This standardized unit of measurement for rack sizes allows IT engineers to easily calculate exactly how much standard equipment can fit on a given server rack. 

Most IT equipment, like rack servers and network switches, also comes in standardized sizes. Standardized rack units reflect that and provide consistency for IT teams across all projects and all spaces.

With that said, most server racks are available in set sizes that can each be applied in different settings and circumstances. The most common server rack sizes are: 

• 12U (21”)
•  24U (42”)
• 27U (47.25”)
• 42U (73.5”)
• 45U (78.75”)
• 48U (84”)

While these are the most commonly used server rack sizes, they are not the only options. Other server rack dimensions, like 18U rack enclosures, are also available, as are custom server rack sizes in specialized cases.

What are the best server rack sizes for your network? That depends on how much space you have and what your needs are.

Finding the Right Server Rack Dimensions 

12U and Smaller

12U and smaller mini server racks are primarily used for small office setups that don’t have a high number of units. If you’re working in a smaller space or only need minimal equipment, 12U racks and smaller sizes are likely right for you.

24U & 27U

24U and similarly-sized server racks can also be used for small office setups, as well as in small or mid-sized closet setups. For slightly larger network setups, like a single branch office, 27U racks are typically the preferred size.

42U

42U server racks are the most common option, and are often the size of choice for high-volume data centers. This is because 42U racks are large enough to fit most servers, routers, and other gear while still allowing ample space for network cabling without being too bulky. However, some servers are too large for 42U racks, so there are some settings that still require larger server rack sizes.

45U-48U

If 42U server racks aren’t enough, 45U and 48U racks are the two most common sizes. 48U is the more common choice, as it is seen as the best option for large-scale data centers. 48U racks can hold most of the bulkiest equipment available, and often still provide IT teams with even more space to grow and add more hardware as needed.

Need More Help With Server Rack Dimensions?

If you are still unsure what the best server rack dimensions are for your office or server room, our knowledgeable team can help. Rackfinity offers expert data center and IT solutions, as well as access to industry-leading IT equipment. 

Browse all of our rack enclosures, or contact us if you have any questions about server rack sizes or any other IT concerns.