Rack Unit Calculator


Rack unit calculator

What is rack unit calculator?

Knowing how much Rack Unit space you require is very important when installing 19" Rack Cabinets & Enclosures. The 19 Inch Rack Calculator below can convert inches and mm into Rack Units. It can also convert Rack U's into Inches and mm. This is a very useful tool for any installer or musician who needs to know exactly what equipment to buy when building a 19" Rack. Each U or Rack Unit is equivalent of 1.75" and is used as the standard terminology for describing sizes with 19 inch rack cabinets.

What is a “U” or “Rack Unit”?

A rack unit (abbreviated as U, less commonly seen as RU) is a unit of measurement applied to equipment racks and the servers, disk drives and other devices that they contain. One U is 1.75 inches (44.45mm); the standard rack, at 19 inches, is 42U.

Rack servers and other hardware designed to be rack-mounted are manufactured in multiples of 1.75 inches and specified in multiples of rack units, usually 1U, 2U, 3U or 4U. Racks are designed to hold equipment of those sizes. The holes in the mounting flanges of racks are arranged in groups of three, and that three-hole grouping is also called a rack unit.

Rack units for equipment is considered maximum dimensions. In practice, devices are often made slightly smaller than the specified U value to allow a little space. A device specified as 2U, for example, may in reality measure 3.44 inches in height, rather than the 3.5 inch multiple of 1.75.

Rack unit calculator grid:

Rack Units
Height (in)
Height (ft)
Height (cm)
1U
1.75″
0.15′
4.4 cm
2U
3.5″
0.29′
8.9 cm
3U
5.25″
0.44′
13.3 cm
4U
7″
0.58′
17.8 cm
5U
8.75″
0.73′
22.2 cm
6U
10.5″
0.88′
26.7 cm
7U
12.25″
1.02′
31.1 cm
8U
14″
1.17′
35.6 cm
9U
15.75″
1.31′
40 cm
10U
17.5″
1.46′
44.5 cm
11U
19.25″
1.6′
48.9 cm
12U
21″
1.75′
53.3 cm
13U
22.75″
1.9′
57.8 cm
14U
24.5″
2.04′
62.2 cm
15U
26.25″
2.19′
66.7 cm
16U
28″
2.33′
71.1 cm
17U
29.75″
2.48′
75.6 cm
18U
31.5″
2.63′
80 cm
19U
33.25″
2.77′
84.5 cm
20U
35″
2.92′
88.9 cm
21U
36.75″
3.06′
93.3 cm
22U
38.5″
3.21′
97.8 cm
23U
40.25″
3.35′
102.2 cm
24U
42″
3.5′
106.7 cm
25U
43.75″
3.65′
111.1 cm
26U
45.5″
3.79′
115.6 cm
27U
47.25″
3.94′
120 cm
28U
49″
4.08′
124.5 cm
29U
50.75″
4.23′
128.9 cm
30U
52.5″
4.38′
133.4 cm
31U
54.25″
4.52′
137.8 cm
32U
56″
4.67′
142.2 cm
33U
57.75″
4.81′
146.7 cm
34U
59.5″
4.96′
151.1 cm
35U
61.25″
5.1′
155.6 cm
36U
63″
5.25′
160 cm
37U
64.75″
5.4′
164.5 cm
38U
66.5″
5.54′
168.9 cm
39U
68.25″
5.69′
173.4 cm
40U
70″
5.83′
177.8 cm
41U
71.75″
5.98′
182.2 cm
42U
73.5″
6.13′
186.7 cm
43U
75.25″
6.27′
191.1 cm
44U
77″
6.42′
195.6 cm
45U
78.75″
6.56′
200 cm
46U
80.5″
6.71′
204.5 cm
47U
82.25″
6.85′
208.9 cm
48U
84″
7′
213.4 cm

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