What height should my network or server cabinet be?

The interior height, which is important for usability, is measured in U (height unit) in an internationally standardized way. 1 U is 44.45 mm. The OUTSIDE height of the cabinet is then defined by the roof and floor construction of the respective cabinet type.

Some standard dimensions have become established: cabinets with an external height of 1200 mm usually have a useful height inside of 24 or 25 U. At 2000 mm external height, the usable internal height varies between 41 and 43 U depending on the manufacturer.

You calculate the cabinet height and useful height you need by:

  1. First, convert the height of all fixtures whose height is not specified in height units (U) into height units. These include stand-alone UPS, desktop computers, etc.
  2. Add the value obtained to the U value of the other fixtures. Theoretically, the useful height of your cabinet would now be determined, but in practice it has proven useful to add some “buffers”. So you should
  3. Allow about 1-2 U of free space between servers and internals, which generate a relatively large amount of waste heat, so that they do not heat each other up.
  4. Even if you want to install fans (units) in the floor or roof, you should leave 2-3 U of free space there to achieve good airflow and thus optimal air circulation.
  5. Now you have a reference value for the useful height in U. An important final consideration should be future-proofing. Is it foreseeable that in the future other internals will take a place in your network or server cabinet? Then it would make sense to buy a cabinet with a little more useful height, so as not to have to replace the cabinet a short time later. This saves work and money.

In short:
Height of all fixtures
+ free space between servers
+ free space for fans
+ future proof
= useful height