Duct Hanger Load and Count
The weight each duct hanger carries at a chosen spacing and the count a run needs.
Example
You enter
- Duct weight per foot (lb/ft) 5.5
- Hanger spacing (ft) 8
- Run length (ft) 40
You get
- Load per hanger (lb) 44
- Hangers for the run 6
Details, formula, and sources
load = per-foot weight x spacing; count = ceil(run / spacing) + 1. A duct at 5.5 lb/ft on 8 ft centers puts 44 lb on each hanger, and a 40 ft run takes 6 hangers; a heavier lined duct at 9 lb/ft on 10 ft centers is 90 lb/hanger over 5 hangers - wider spacing means fewer hangers but more load on each. SMACNA sets the max spacing (~8-10 ft rectangular); large duct goes on a trapeze.
load_per_hanger_lb = duct_lb_per_ft x spacing_ft; count = ceil(run_ft / spacing_ft) + 1; utilization = load_per_hanger_lb / hanger_swl_lb.
Duct-hanger load / count identity by name (tributary weight per hanger; count from run and spacing); first-principles statics.
The tributary-load statics are public first-principles; the max spacing (SMACNA) and hanger SWL come from SMACNA and the manufacturer.
Estimate. AHJ and licensed professional govern.
Field names used by the API: duct_lb_per_ft, spacing_ft, run_ft, load_per_hanger_lb, count
- Max spacing ~8-10 ft for rectangular duct per SMACNA; entered hereSMACNA duct construction standards
- Per-foot weight from duct-metal-weight, plus wrap and any water in a coilduct-metal-weight