Timber Truss Design Calculator
King-post truss member forces, rafter sizing, and bottom chord tension from span, rise, and loading.
Inputs
ft
ft
psf
ft
in
in
Results
Rafter axial force
6,923 lbs
≈ 7 grand pianos
Bottom chord tension
2,880 lbs
≈ 16 adults
King post tension3,840 lbs
Horizontal thrust2,880 lbs
Rafter compression capacity48,000 lbs
Rafter utilization ratio0.14
Min bottom chord size2.1 in
Min king post size2.4 in
Pitch angle33.7°
Pitch (x:12)8:12
Rafter length14.42 ft
Total load on truss7,680 lbs
How to Use This Calculator
- Enter Truss span, Truss rise, and Total roof load.
- Set Truss spacing, Rafter width, and Rafter depth.
- Adjust Wood species as needed.
- Review Rafter axial force (lbs) and Bottom chord tension (lbs).
- Use King post tension (lbs) and Horizontal thrust (lbs) to inform your decision.
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