Wood Roof Truss Calculator — m, lumber
How to use this calculator
Select a truss type, enter the span, roof pitch (degrees), truss spacing, and building length. Choose chord and web member sizes. The calculator computes truss height, rafter length, number of trusses, and total volume of lumber in m³.
Truss types — King Post (simple, short spans), Queen Post (medium spans), Fink/W (most common residential), Howe (heavier loads).
Lumber — volume = width(m) × depth(m) × length(m).
Saved Calculations
| Time | Type | Span | Pitch | Trusses | Total m³ | Cost |
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How to Calculate Wood Roof Truss Lumber (Metric)
This calculator estimates lumber volume for common residential roof truss types per EN 1995-1-1 (Eurocode 5). Enter the building span, roof pitch in degrees, truss spacing, and building length. The calculator determines the number of trusses, rafter length, truss height, web member count, and total timber volume in m³.
Formulas
Rise = (span/2) × tan(pitch). Rafter = (span/2)/cos(pitch) + overhang/cos(pitch). Trusses = building length / spacing + 1. Volume = width(m) × depth(m) × length(m) for each member.
FAQ
What spacing should I use? 600 mm on centre is standard. 400 mm for heavier roof loads or longer spans.
What are typical member sizes? For spans up to 8 m: 38 × 140 mm chords, 38 × 89 mm webs. For longer spans: 38 × 184 mm or 38 × 235 mm chords.
