Build and print a front or rear 19-inch server or network rack layout with U-position validation, no signup, and local browser processing.
Drag a preset to a U, or tap it to add at the first open position. Presets remain fully editable.
CSV columns: name,height_u,start_u,face,depth_mode,depth_in,category,weight_lb,power_w,airflow,rail_min_in,rail_max_in,notes. Required: name and height_u. Valid rows load even if others have errors.
Share links use #rack=<base64url-encoded versioned JSON>. The fragment stays client-side; use JSON export for layouts too large for a reliable URL.
Front face. Drop equipment on an open U; blocks snap to whole units.
Select a block or add equipment from the library.
Start U is the lowest occupied U when U1 is at the bottom, or the top occupied U when U1 is at the top.
| U | Front | Rear | State |
|---|
Each example is loadable from the template buttons above. Exact U ranges are listed using U1 at the bottom; reserve and utilization totals recalculate when loaded.
Reserve: U11–U12. Placed: 10U of 10 usable U (100%, including one blanking panel).
Heavy UPS equipment stays low; the patch panel and cable manager sit together; U10 closes an intentional opening.
Reserve: U22–U24. Placed: 21U of 21 usable U (100%, including 3U of blanking panels).
Pairing panels with horizontal management shortens patch-cord paths. The top reserve leaves a visible growth zone.
Reserve: U39–U42. Placed: 32U of 38 usable U (84.2%).
Low heavy equipment and front-to-rear airflow are planning choices, not universal rules. Vendor rails, facility loading, cooling, redundancy, and maintenance access decide the final layout.
Front and rear elevations: use the face tabs to document what a technician sees at each rail set. Full-depth equipment occupies both faces; the planner permits front and rear half-depth devices to share a U only when their combined depths fit the cabinet allowance.
U numbering and start position: Advanced settings supports ascending labels (U1 at bottom) or descending labels (U1 at top). For a multi-U device, Start U means the lowest occupied label in bottom numbering and the top occupied label in top numbering; the helper beneath the selected device repeats this convention.
0U equipment: choose 0U side for compatible vertical PDUs or cable managers. They appear outside numbered space, but still contribute to weight and power totals and require side/rear clearance.
Cabinet depth versus rail depth: cabinet depth is the overall enclosure planning envelope; usable rail depth is the front-to-rear mounting-post spacing. Device rail minimum and maximum values are compared with the rail-depth control. Rear cable allowance is separately checked against equipment depth.
Cable bend and airflow: rear allowance is a planning proxy, not a vendor bend-radius validation. Mixed active airflow directions are review items. Fill unused front openings with suitable blanking panels where the cooling design calls for them.
Growth and capacity: top/bottom reserves protect planned space, while blanking panels visibly occupy current gaps. U capacity is not power, cooling, weight, floor loading, or service capacity; compare all four summary and warning areas.
The model uses 1U = 1.75 in = 44.45 mm, converts displayed labels to physical bottom-up coordinates, and checks every device span against rack boundaries, reserves, same-face equipment, and full-depth equipment. Opposite-face half-depth sharing is accepted only when combined device depths plus front and rear allowances do not exceed cabinet depth.
Weight and power are summed when supplied. Rail ranges, rear cable clearance, mixed active airflow, heavy devices mounted in the upper half, and unfilled front openings are reported as review items—not certified failures. The browser cannot know rail-kit geometry, door swing, cable bend radius, cooling performance, floor loading, seismic design, electrical protection, or local code.
Accountable publisher: Starlight Robotics. No individual technical reviewer or third-party endorsement is claimed.
Reviewed: 17 July 2026. Planner version: 2.0.
Test cases: boundary placement at U1 and top U; same-face collision; full-depth face collision; valid and invalid half-depth sharing; 0U placement; reserve overlap; rail range; negative rear clearance; weight/power limits; CSV partial import; JSON round trip; undo/redo; 12U, 24U, 42U, and 48U templates.
Change log: v2.0 added visual editing, front/rear and 0U models, practical constraints, templates/library, import/persistence, accessible rack output, and diagram exports.
Add the U heights of current equipment, cable managers, and blanking needs, then include a reasonable growth reserve. Also verify power, cooling, weight, rail depth, service clearance, and facility rules; vertical U capacity alone does not determine rack size.
The arithmetic maximum is 42 one-U servers or 21 two-U servers when every U is available. Real layouts usually fit fewer after switches, patching, power, cable management, airflow, weight, and growth allowances.
It has 42 numbered rack-unit positions, but reserves, structural features, installed accessories, cable routing, doors, and site requirements can reduce the positions practical for equipment.
With U1 at the bottom, start U means the lowest occupied U. With U1 at the top, it means the top occupied U. The planner states this convention beside the control and converts it to physical positions internally.
Yes when the rack and device support it. This planner models front, rear, full-depth, and compatible half-depth sharing, but manufacturer rails, access, airflow, cabling, and clearances still control the actual installation.
A common planning starting point is 20 to 30 percent, but the right reserve depends on expected growth, redundancy, patching, airflow strategy, budget, and facility standards.
Yes. Export or prepare a CSV with the published columns, then import it. Valid rows are kept and row-level errors are reported. JSON import restores the complete editable planner state.
Yes. The print view is PDF-friendly and includes rack identity, face, U labels, equipment legend, capacity totals, date, revision, and unresolved warnings. PNG and SVG diagrams are also available.
This tool creates documentation and review prompts; it does not certify an installation. Confirm the final design with equipment and rack manufacturers, facility owners, electrical and cooling designs, load ratings, applicable codes, and qualified installers.
Starlight Tools