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Rack Unit (RU) Planner

Stack equipment into rack units, apply growth space, and see how many racks the room actually needs.

Equipment total21 RU
With 25% reserve27 RU
Racks required (42U)1
Resulting fill per rack64%

RU math checks space only — power, cooling, and weight are separate (and less forgiving) checks.

Methodology

Where the math comes from.

How it works

List the equipment going into the room — patch panels, switches, fiber enclosures, UPS, shelves — with their rack-unit heights and quantities. The tool totals the RU, applies the growth reserve you choose, and divides into standard rack heights (42U/45U/48U) to show how many racks the space needs and how full each lands.

Why growth space is a line item

A rack planned at 100% on day one fails its first move-add-change. Reserving 20–30% — as deliberate, labeled space, not leftover gaps — is standard practice for a room that has to live a decade. The reserve also absorbs the things plans forget: wire management that grows with density, future fiber trays, the UPS that gets bigger.

What the tool deliberately ignores

Heat, power, and weight. A 42U rack of switches is a power and cooling problem long before it is a space problem — RU math is necessary, not sufficient. Equipment power budgets, UPS runtime, and airflow design belong in the real telecom-room design (and they are exactly the items a peer review checks).

FAQ

Asked about this one.

42U is the common full-height standard (about 6.5 ft of usable mounting space); 45U and 48U variants buy more density where ceiling height and delivery paths allow. Wall-mount and half-height cabinets run anywhere from 6U to 24U.
A 20–30% deliberate reserve is the common planning band for commercial work. Mark it on the elevation as reserved space rather than leaving it implicit — unlabeled gaps get consumed by the first contractor who needs somewhere convenient.
Common formats: 24-port panels at 1U, 48-port at 2U (or high-density 1U), fiber enclosures 1–4U by capacity. Add horizontal wire management — typically 1U per 1–2 panel units — or the elevation that looked efficient on paper becomes unmanageable in service.
Deliberately not — RU math tells you if equipment fits the rack, not whether the room can power and cool it. Those come from equipment power budgets and the mechanical design, and skipping them is one of the most common findings in our design reviews.
Next step

The calculator sketches it. The design defends it.

When the number has to survive plan review, bidding, and closeout testing — that's RCDD design work, and it's what we do.

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