About This Calculator
This calculator helps you estimate the number of timber members needed for framing walls, floors, or decks. You can enter an explicit count or provide an area with spacing to auto-calculate.
Results include linear metres, cubic metres, and board feet to suit both metric and imperial ordering systems.
Common Spacings
| Application | Spacing |
|---|---|
| Stud walls | 400 mm (16") or 600 mm (24") |
| Floor joists | 400 mm (16") typical |
| Roof rafters | 400-600 mm (16-24") |
| Decking joists | 400 mm (16") |
Tips
- • Add 10% wastage for cuts, defects, and waste
- • Check standard stock lengths to minimise offcuts
- • Board feet (BF) = thickness (in) × width (in) × length (ft) / 12
Ready to Calculate?
Enter member count or area with spacing to get quantities.
Open CalculatorRelated Calculators
UKUK Building Regulations
References & Sources
Standards Cited
- BS EN 14081 — Timber structures — Strength graded structural timber
Defines grading rules and standard dimensions for structural timber in the UK - BS 5268-2 — Structural use of timber — Code of practice for permissible stress design
Guidance on timber selection and sizing for structural applications
Formulas Used
- Member count (area-based):
count = ceil(perpendicularSpan / spacing) + 1
Source: BS 5268-2 — Perpendicular span = area / member length; +1 for the end member - Total linear length:
totalLength = memberCount × memberLength
Source: Basic geometry - Volume:
volume = totalLength × crossSectionWidth × crossSectionDepth
Source: Basic geometry
Key Assumptions
- Timber sizes use finished (planed) dimensions: e.g. 47 × 75 mm — BS EN 14081
- Standard timber lengths: 2.4m, 3.0m, 3.6m, 4.2m, 4.8m — UK timber merchants standard stock