Colocation Rack Sizes – How Many U Do You Need?

Colocation Rack Size

The economic viability of colocation hosting services has recently seen most businesses turn away from traditional web hosting infrastructure. And why not? With most companies owning IT server hardware to handle their ever-increasing data storage needs, colocation hosting provides the ideal opportunity for housing these servers securely and at a low cost.

That said, colocation services can only be beneficial if you find a data centre that offers the right rack size for your servers. This way, you only pay for the space you need, helping you save money.

This piece discusses the various rack sizes and what to consider when choosing a rack. Understanding these variables should help you purchase a rack that suits you best as you transition to colocation hosting services.

What are Server Racks

A server rack refers to a steel cabinet or framework specially designed to store your servers, cables and other IT hardware in a way that optimizes floor space use while maintaining optimal server performance.

Not to be confused with server towers that are designed upright, server racks have a low-profile enclosure and are sturdily built with several cooling systems. Server racks also have patch panels, switches and prefabricated slots for connecting electrical and internet cables.

Besides, the server rack bay allows you to securely stack your servers and IT equipment while also enabling easy airflow control.

How to Calculate Server Rack Size and the U space

While there are various types of server racks — some may be open frame, locked or customized — the main classification comes down to server racks size. This is because server cabinets are built depending on the size of the IT equipment to be stored. The main components to consider when calculating the rack size are;

  • Rack height

Data centres label their racks according to their size. The rack sizes are commonly measured in Rack Units (U), where one rack unit equals 1.75 inches.

As a result, it is common practice for servers and IT hardware to be built in multiples of 1.75 inches to enable easy rack height calculations. The standard size frame for a server rack is 48U, which is ideal because it allows for dense hardware configurations while optimizing floor space use.

That said, data centres will offer you varying rack sizes depending on the size of your servers and other IT hardware. You can go for;

  • Full rack (typically 42U)
  • Half rack (typically 21U)
  • Quarter rack (typically 10U)

However, if you need much smaller or larger rack space, consider the non-standard open frame racks that can go up to 70U or be as small as 5U.

  • Server Rack Depth and Width

Rack depth is mostly measured in inches. Server rack depth will mostly range between 24 and 48 inches. Racks have rails along their depth, allowing for adjustable mounting of your IT equipment.

Most standard server racks have an internal 19-inch width to allow for seamless mounting of servers. Besides, they have a 24-inch exterior width to allow them to take up exactly one-floor panel in a data centre. This width leaves enough space to manage switches and cables and carry out hardware maintenance.

Now that you know the standard server rack sizes available, you can easily factor in the amount of space your server and IT hardware will require, then calculate the rack size needed. When calculating the right rack size, remember to factor equipment taller than 1U and the need for airflow control space.

What to Consider when Choosing Your Server Rack Size

As we’ve seen, the size of servers and IT hardware you want to store is critical to determining your ideal server rack size. However, factors such as security, ventilation and customizability of your server racks also affect the size of your rack. Let’s look at the major considerations:

1. Flexibility and Expansion of the Server Rack

With digital transformation on a rapid rise, you will likely expand your IT infrastructure in the near future, hence requiring larger server racks. Therefore, it is worth going for a much larger rack than you need now so that there will be less hassle finding space for new hardware.

You are probably worrying if this is economically viable. Well, we have colocation hosts that offer a pay-as-you-grow service. The data centre allows you to take a full rack but only charges you for your current rack size, with the promise that you’ll fill up the rack in the future.

2. Security

Colocation host services recommend that you share a rack with other companies if your hardware requires less than a quarter rack. While this may be cheap, it also compromises the security of your servers.

It is advisable to take a fully enclosed server rack for optimum security.

3. Power Draw of Your IT setup

If your IT hardware requires multiple cable connections, it may be ideal to go for a larger rack with enough space and power supply to keep your servers running without affecting the airflow.

4. Enclosements and Ventilation

Are you going for an enclosed or open-frame rack? Open frame server racks are easy to assemble and provide maximum ventilation for dissipating excess heat. Therefore, having a large open server rack will reduce overheating while providing enough space for your hardware. The only downside to an open frame rack is that it exposes your servers to the external environment.

That said, we also have enclosed server racks with removable perforated doors and adjustable mounting rails that allow you to install and take out IT hardware. The perforated doors provide ventilation while also keeping the servers secure.


Migrating your IT hardware to a colocation host service has multiple benefits. However, choosing the ideal server rack size will go a long way to saving you money and ensuring your IT infrastructure works optimally.

That said, you need a server rack size that guarantees hardware security, proper rack ventilation and allows for future expansion.