c0de.it/docs/rack-planner/cable-length.md

Cable Length Calculation

Goal

Estimate practical cable lengths from the physical arrangement of devices in a rack so users can preselect realistic patch and power cable variants.

The result should support planning, not exact installation certification.

Use cases

• patch cable length between patch panel and switch
• DAC or fiber estimate between devices in the same rack
• power cable estimate from PDU to active device
• BOM generation for preconfigured cable sets

V1 approach

Cable length should be estimated from:

• rack unit position of both components
• side of connection: front or rear
• optional port offsets
• route style
• slack factor

Suggested routing model

For V1, use a rule-based path estimate instead of full geometric routing.

Inputs

• source component U position
• target component U position
• source and target side
• rack depth
• routing preference
• slack percentage or fixed reserve

Routing preferences

• front_vertical
• rear_vertical
• front_to_rear
• shortest_practical

Example calculation logic

Estimate length as:

1. vertical distance between source and target mounting positions
2. plus horizontal or side transition allowance
3. plus front/rear traversal allowance
4. plus slack reserve

Illustrative formula:

estimated_length =
  vertical_distance_mm
  + side_transition_mm
  + front_rear_allowance_mm
  + service_loop_mm

Then round up to the next marketable cable length, for example:

• 0.25 m
• 0.5 m
• 1.0 m
• 1.5 m
• 2.0 m
• 3.0 m

Accuracy strategy

The tool should display:

• raw estimated length
• recommended order length
• confidence note such as estimate only

Data requirements

Better cable estimation becomes possible if components expose ports with offsets.

Minimum V1:

• component U position only

Better V1:

• per-port offsets in the component metadata

BOM integration

Cable entries can be generated as:

• one line per connection
• or aggregated by cable type and recommended order length

Example:

• 12 x RJ45 patch cable Cat6A, 0.5 m
• 4 x C13 to C14 power cable, 1.5 m

Future improvements

• front and rear cable manager objects
• reserved routing channels
• left/right side path selection
• bend radius constraints
• color-coded cable groups
• cross-rack cable planning