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How Many 1U Servers will Fit in a Rack?

Posted by QuoteColo on November 01, 2013 - Updated on January 29, 2020

How Many 1U Servers will fit in a Rack

A Primer on Server Racks

If you are new to the web hosting colocation industry, you are going to need to get a lay of the landscape and learn some of the basics. Those basics include understanding what 1U means, what a rack is, how many 1U servers can fit in a rack, the different sizes of racks and why power is a large factor in how many servers can fit in a rack. If you own a 1U server and do not want to host it at home/office, you may want to consider a colocation service which can offer you rack space, redundant power and Internet. Pricing starts at $29.99 a month for 1U, 1Amp 120V and 3TB bandwidth.

So, first things first, what is 1U?

The Standard Rack Unit

Like any basic form of measurement, within the colocation industry there is a standard size for servers. This size of each server is called a U or a RU (Unit or Rack Unit). For the sake of standardization, the size of a single U or RU is 1.75 inches in height (44.45 mm). With 1U equaling 1.75 inches in height, each successive U size, 2U, 3U, 4U and so on refers to the overall height of mounted (racked) servers.

What is a Server Rack? 

Just like standard colocation server sizes, there are also standard rack sizes. For those of you who don’t know, the rack is the metal frame that acts as server infrastructure. This infrastructure comes in a few dimensions.

  • Full Rack – A full rack of servers is equal to 42U or roughly 6 feet of racked servers.
  • Half Rack – A half rack of colocation servers is equal to roughly 18U – 22U, or slightly over 3 feet of stacked servers.
  • Quarter Rack – A quarter rack colocation, sometimes called a ¼ Rack, refers to a rack which typically holds 10U – 12U, or roughly 1.5 feet of servers.

It should be noted: in terms of the colocation world, a half rack has a slightly different meaning than a simple calculation of half the server space. Within the data center colocation world, a half rack is a unit which is 1U in height with only half the depth of a typical 4-post rack. The benefit of a half rack is that it allows for two 1U servers to be mounted side by side as opposed to one under the other.

Why Different Colocation Rack Sizes?

The reason why colocation pricing racks come in varying sizes with standard U or RU dimensions is two fold: for the provider, different racks sizes allow for larger services to be provided, i.e. higher costs. From the consumer’s point of view, having the ability to grow into a full rack or a cabinet is a matter of future expectations. While the size of racks is partially determined on power needs from the consumer aspect, more often than not the decision to purchase an entire rack as opposed to a half rack or a quarter colocation rack is based on projections for growth.

Per U Colocation Pricing Models

As a colocation broker, QuoteColo has facilities all around the world that offer per U colocation. Pricing starts from $50 a month USD. That price includes standard power and a specific amount of monthly bandwidth burstable from 100Mbps to 10Gbps. Similar to real estate, it is all about location. On the USA East Coast, per U pricing seems to be much higher.

Feel free to contact us on the form above or sales (at) if you have additional questions or would like a custom price quote.


One Comment

  1. ReemJanuary 22, 2019 at 5:10 am

    so the 42 U server fits 24 server inside the rack, right?


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