Plan a rack before you order the rail kit.
Stack servers, switches, storage, and a UPS into a rack and check three budgets that actually stop a rack build: U-space, circuit power (with the NEC 80% continuous-load derate applied automatically), and weight.
A first-pass budget check, not a substitute for a real rack elevation drawing — it doesn't model airflow, cable routing, or rail/depth clearances. The same spirit as the Engineering Calculators and the POD & Skid Designer.
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Component detail
Why these checks
U-space
The most obvious budget and the easiest to blow: total rack units used can't exceed the rack's physical height. Blanking panels and cable managers count against U-space too — they're often left off a first-pass equipment list and then the rack comes up short.
Circuit power, with the 80% continuous-load derate
NEC 210.19 and 210.20 (and the equivalent CEC rule) require a continuous load — running 3 hours or more, which describes nearly all rack IT load — to stay at or under 80% of a branch circuit's rating. A 20A/208V circuit is rated 4,160W but its continuous-load-safe budget is 3,328W, not 4,160W. This tool applies that derate automatically rather than checking against the raw circuit rating, the same convention used on the Engineering Calculators page.
Weight
Rack weight ratings vary a lot by frame construction and floor loading — confirm the actual rating on the rack's own spec sheet and against the room's floor load capacity, especially for a raised-floor data hall. This tool's default (1,500 lb) is a reasonable placeholder for a standard 42U enclosure, not a universal number.
Common questions
Why does the power check apply an 80% derate?
NEC 210.19 and 210.20 require continuous loads (3+ hours, which describes nearly all rack IT load) to stay at or under 80% of a branch circuit's rating. A 20A/208V circuit is rated 4,160W but its continuous-load-safe budget is 3,328W. This tool applies that derate automatically.
Is this a substitute for a real rack elevation drawing?
No. It's a first-pass budget check using simplified assumptions — it doesn't model airflow, cable routing, or physical rail/depth clearances. Always confirm against the rack manufacturer's spec sheet and a real elevation drawing before ordering.
Is this free and does it require an account?
Yes — free, runs entirely in your browser, no signup. Nothing you enter is sent anywhere.