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Data Center Server Rack Sizing Guide

What Size Should My Server Rack Be?

Data centers run on server stacks, and they are usually stored in server racks. So, if you need a lot of processing power and/or data storage, then you’ll need to understand rack sizes in order to strategize.

Unfortunately, server racks are not measured according to specific official dimensions. Fortunately, they are standardized, and you can read those standards when you understand the measuring unit utilized across the industry.

This quick guide will explain how racks are measured and what you need to know in order to pick the correct server rack for your operation.

The Unit U

The first thing to know about server rack sizing is that there is a standard unit just for this purpose: U. This unit measures the height of the rack and 1 U is equivalent to 1.75 inches.

That might seem like an obscure number, but it’s an appropriate increment for measuring the number of device units that are in a rack. Each “U” can sufficiently hold one server unit.

What you might notice is that this number only measures the height. That’s because the length and width of server racks are far less important than the height. Racks typically stack units in a vertical fashion, so the number of Us in a rack tells you how many server units can be stacked on top of each other.

You can certainly find custom builds that don’t fit into the standard, but for the most part, server racks are measured in these increments.

42U Racks

42 U is one of the most common rack sizes that you will be able to find. Such a rack is 73.5 inches tall, or about 6 foot 1. This rack size is ideal for maximizing vertical space while still fitting inside of standard ceiling heights. Additionally, these racks can be serviced by many technicians without the need of ladders or other equipment.

48U Racks

Another common rack size is 48 U. Such a rack is 84 inches tall or 7 feet tall exactly. These racks are common because they open up a little more vertical space than the 42 U option. While they might require ladders or other devices to service, they still fit easily inside of 8-foot ceilings, which are a common ceiling height in many buildings.

Other Rack Sizes

The 42 and 48 U racks are very common, but they’re hardly the limit of your options. A few other fairly typical rack sizes include 22, 27, and 52 U. These shorter racks are great in facilities that are not extremely limited in square footage. They are also easier to move, install, and service, lowering overall associated labor costs.

Outside of these normalized sizes, you can get very tall server racks that are ideal for warehouse settings. The maximum size you will typically find is about 70 U. That is 122.5 inches or over 10 feet in height. Such racks certainly require more care for service, but they can fit much more processing power and data storage into a square foot of warehouse space.

As you can see, sizing data center server racks is pretty straightforward. Most racks will use the standard unit, U. When that is the case, you can multiply the unit number by 1.75 to get a rack height in inches, and you can use that to verify that the rack will fit in your space.

Regardless of the specific application, if you need server racks, then you will need multiple stacks. It’s important to figure out just how high you will be stacking your equipment to inform your budget and purchasing options.

Additional Learning Center Resources