Rack Unit Calculator (leasing rack space in cabinets)

By , November 22, 2013

The “Rack Unit” is a standard measurement for server height; one rack unit (U) is 1.75 inches.

When leasing space in a colocation facility (or planning for an on-site network cabinet or closet), customers should focus on four key issues:

  1. space: cabinet or rack width is almost always 19 inches; depth may range from “less than 30” to “more than 40” inches, and height is measured in “rack units” (below);
  2. bandwidth: 10Mbps, 100Mbps, 1Gbps, 10Gbps; this might be “flat rate” or might impose surcharges when usage exceeds certain levels; also be sure to understand whether your bandwidth is shared with other users on the same switch port;
  3. power: if you lease fractional space in a cabinet, you might be allocated one to five amps (1A to 5A) of power; for a full cabinet, you might be allocated a maximum of 15A to 20A (note that average power usage should not exceed 80% of the total, so 15A max = 12A average).
  4. heat:  You must also pay attention to airflow and cooling; if you lease a full cabinet and fill it completely with equipment, you’ll probably need far more than 15A power, and the heat generated by the equipment might exceed the cooling capacity, causing some equipment (especially at the top) to malfunction.

Here is a “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
Rack Units Height (in) Height (ft) Height (cm)

 

 

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