Roof Truss Calculator — Span, Pitch & Member Sizing
Roof trusses are engineered structural components. This calculator estimates dimensions, quantities, and costs based on span, pitch, and spacing.
Why This Construction Metric Matters
Why: Accurate span, pitch, and loading calculations ensure trusses arrive ready to install.
How: Enter span, pitch, and spacing. The calculator determines truss height, member lengths, and costs.
- ●Standard trusses spaced 24 in. OC; heavy-load areas may require 16 in. OC.
- ●Never cut or modify a manufactured truss without engineering approval.
- ●Trusses must be braced per BCSI during and after installation.
📋 Quick Examples — Click to Load
Planning estimates only. Verify with a licensed engineer or contractor before construction.
📐 Construction Industry Facts
Over 60% of US residential roofs use manufactured trusses.
— SBCA 2023
Engineered trusses can span over 60 feet clear.
— SBCA
Truss uplift can cause ceiling cracks—use truss clips.
— BCSI
Roof trusses are prefabricated structural frameworks that support roof loads efficiently. Peak Height = (Span/2) × (Pitch/12). Top Chord = √((Span/2)² + Peak²). Over 60% of US residential roofs use manufactured trusses. Fink trusses span up to 40 ft; Howe up to 50 ft.
Sources: SBCA, BCSI, TPI 1.
Key Takeaways
- • Peak = (Span/2) × (Pitch/12)
- • Top Chord = √((Span/2)² + Peak²)
- • Bottom Chord = Span + (Overhang × 2)
- • Fink most common; 24 in. O.C. standard
Did You Know?
How Does [Topic] Work?
Peak Height
(Span/2) × (Pitch/12). For 32 ft at 6/12: 8 ft.
Top Chord
√((Span/2)² + Peak²). Pythagorean theorem.
Webs
Vary by truss type; Fink uses W-pattern.
Expert Tips
Truss Type Comparison
| Type | Max Span | Uses |
|---|---|---|
| 🔺 King Post | 26 ft | Residential, commercial |
| 🔷 Queen Post | 30 ft | Residential, commercial |
| ⛰️ Fink | 40 ft | Residential, commercial |
| 🌉 Howe | 50 ft | Residential, commercial |
| ✂️ Scissor | 36 ft | Residential, commercial |
| 🏠 Attic | 32 ft | Residential, commercial |
Frequently Asked Questions
What is a roof truss calculator?
A roof truss calculator estimates truss dimensions, lumber requirements, connector plates, and costs based on span, pitch, and truss type. It supports King Post, Fink, Howe, Scissor, and Attic trusses for planning and budgeting.
How is peak height calculated for a roof truss?
Peak Height = (Span / 2) × (Pitch / 12). For a 32 ft span at 6/12 pitch: (32/2) × (6/12) = 8 ft. The top chord length uses the Pythagorean theorem: √((Span/2)² + Peak²).
What is the maximum span for a Fink truss?
A standard Fink truss spans up to 40 ft. King Post spans ~26 ft; Howe can reach 50 ft. Always verify with a structural engineer for your specific load requirements.
How many board feet of lumber per truss?
A typical 32 ft Fink truss uses 80–120 board feet depending on lumber size. Board feet = (Width × Thickness × Length) / 12. A 2×6 is 1 BF per linear foot.
What spacing for roof trusses?
24 inches on-center (O.C.) is standard for residential. Heavy snow loads or long spans may require 16 in. O.C. Never exceed the truss manufacturer's specified spacing.
Can I modify a manufactured truss?
Never cut or modify a manufactured truss without engineering approval. Modifications can cause structural failure. Contact the truss manufacturer for any design changes.
Key Statistics
Official Data Sources
⚠️ Disclaimer: Estimates for planning. Truss design requires structural engineer approval. Actual dimensions and lumber may vary by manufacturer and load requirements. Not structural advice.
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