Roof Truss Calculator

Calculate the number of roof trusses needed for a building. Enter building length, span, pitch, and truss spacing.

🏠 Roof Truss Calculator

Results

Number of Trusses16 trusses
Roof Rise6.0 ft
Rafter Length13.4 ft
Lumber per Truss26 bd ft
Total Lumber (est.)407 bd ft

πŸ’‘ How to Calculate Roof Trusses

The number of trusses equals the building length divided by truss spacing, plus one for the end. Standard truss spacing is 24 inches on center for residential, 16 inches OC for heavy snow loads. Common truss types include king post, queen post, Fink, and scissors.

Truss span (building width) determines the truss size and lumber requirements. Spans up to 24 feet use 2Γ—4 lumber; 24–36 feet typically use 2Γ—6 lumber. Always consult an engineer for spans over 30 feet or unusual load conditions.

A 30 ft building with 24-inch OC spacing: 30 / 2 + 1 = 16 trusses. For a 24 ft span at 6/12 pitch, each rafter is 13.4 ft long. Estimated lumber per truss: about 35 board feet.

Roof Truss Calculator FAQ

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