Roof Truss Calculator

How many roof trusses do I need?

ft
ft
in
Spacing on center
in

Order this much roof trusses

21trusses

Layout and quantity only. Trusses are engineered to their loads by the manufacturer, and this page does not size them. Ask your truss supplier for sealed drawings and confirm with local code.

28 ft span, 6 in 1221 trusses at 24 in, showing 12. Layout only.
Common trusses19
Gable end trusses2
Top chord length per side16.77 ft
Spacing24 in on center

Count trusses for a gable roof at your spacing and estimate the top chord length.

How it works

Building length in inches รท spacing, rounded up, plus one. Two of those are gable ends. Top chord length uses the slope multiplier.

Before you order

  • Order from a truss plant with the span and loads on the drawing.
  • Brace trusses during install as the engineer specifies.
  • Never cut or drill a truss without engineer approval.

Common questions

Does this calculator design trusses?

No. It counts them. Truss design needs sealed drawings from the manufacturer.

What spacing do trusses use?

Often 24 inches on center, set by the truss drawings.