Free tool
Server Rack Space Planner
Add up the rack units, depth, weight, power draw and heat output of your equipment, and see which cabinet size actually fits it with room to grow.
Add what is going in the cabinet and this works out the rack units used, the depth and weight it has to carry, the power it draws and the heat it puts into the room. Four separate things decide whether a rack is the right one, and height is only the first of them.
Rack elevation
Depth is what catches people out
A cabinet is advertised by its height in rack units, so that is the only figure most people check. Depth is what actually stops the door closing. A wall mounted cabinet is often 450 or 600 millimetres deep, and a modern server is 750 or more before you add the power cables and network leads bending out of the back. The deepest single item in your list sets the cabinet you need, not the average, and the figure above adds an allowance for cable bend radius behind the equipment because that space is not optional.
Weight, especially on a wall
Batteries and servers are far heavier than they look. A UPS with its battery pack can exceed a hundred kilograms on its own, and that load is hanging off the front rails on a cantilever. Wall mounted cabinets are typically rated around 60 kilograms of equipment, which a single UPS will exceed by itself. If the total above is more than that, the answer is a floor standing cabinet, and the heavy items belong at the bottom rather than wherever there was a free gap.
Heat is the quiet failure
Every watt drawn ends up as heat in the room, which is what the BTU figure is telling you. A rack drawing a kilowatt is a one kilowatt heater running permanently in a cupboard, and in a Lebanese summer that cupboard will reach temperatures where equipment throttles, then fails early, long before anything looks obviously wrong. Equipment rarely dies at once from heat. It ages quickly, disks fail more often, and the pattern is only clear in hindsight.
If the figure is above a few hundred watts, the room needs either real ventilation or dedicated cooling, and the cabinet needs clear airflow front to back with blanking panels in the empty spaces. Blanking panels feel like a pointless expense and are the cheapest cooling improvement available, because without them hot exhaust air simply loops around the front of the equipment and gets breathed in again.
Leaving space on purpose
A cabinet filled to capacity on day one is a cabinet that has to be emptied and rebuilt the first time anything is added. Twenty percent spare is the usual allowance, and it should be left at the top and bottom rather than scattered as single gaps, because most additions need two or three units together. The same applies to the patch panels: terminating every port on day one costs almost nothing extra, while adding one later means pulling cable through a rack that is already dressed and tied.