What is a rack unit (U)?
A rack unit, written U, is the height of one slot in a rack. Everything in a rack is sized in whole units.
Most mini PCs, Macs, modems and small switches can't go in a rack on their own. When you add one, the planner puts it in a rack mount made to fit that exact device, from 3D Rack Mounts. Gear that already has rack ears goes straight in.
Tap an open slot to choose where the next item goes. Drag an item to move it (on a phone, press and hold first). Tap it to remove it.
1U is 1.75 inches
One rack unit is 1.75 inches tall. 2U is 3.5 inches, 4U is 7 inches. The width of the rack (10 inch or 19 inch) doesn't change the height of a U.
Counting what you need
Add up the U of every item: a 1U switch, a 1U patch panel, a 2U NAS and a 2U UPS make 6U. Gear without rack ears takes the U of its mount; the planner shows that for you. Then add 1U to 2U of room to grow.
Picking a rack height
Racks are sold by U: 6U, 8U, 12U and so on. Pick the next size up from your count. A rack that is too tall is only a little more space; one that is too short means starting over.
Questions
- How tall is 1U?
- 1.75 inches.
- Is a U the same in 10 inch and 19 inch racks?
- Yes. Only the width is different.
- How do I know how many U a device takes?
- Rack gear lists its U. For gear with no rack ears, search it in the planner: it shows the U of the mount made for it.
More guides
How it works
- Pick a rack. 10" mini racks (DeskPi, GeeekPi, Lab Rax and similar) or a standard 19" rack, at the height you have.
- Add your gear. Search a device to place it. Gear that already has rack ears, like UniFi and Netgear switches, Synology RackStations, UPS units and PDUs, is in the list too and goes in as rack-ready.
- See what's missing. Anything without ears shows as "needs a mount", with a mount you can buy for it.
- Share it. The link holds the whole layout, so a build can be posted, compared or finished later.