Lumber Calculator – Fast, Accurate Material Estimates
Use this free lumber calculator to size materials for common projects. Whether you’re framing a room, running skirting or fascia boards, or laying down sheets of plywood/OSB, this tool gives you quick piece counts, board feet (BF) or cubic meters (m³), estimated offcuts, and optional cost. It supports both metric and imperial units and uses real-world defaults with editable waste.
How the Lumber Calculator Works
- Nominal vs actual sizes: You pick the nominal size (e.g., 2×4 or 90×45). The calculator uses the actual finished dimensions to compute volume precisely.
- Board feet / m³: Imperial projects use board feet (BF), calculated from thickness × width × length ÷ 144. Metric projects use cubic meters (m³).
- Waste allowance: Add 5–15% to cover trim cuts, knots/defects, and handling losses. You control the percentage.
- Stock lengths: Choose the lengths you can actually buy. A simple greedy optimizer packs cuts to reduce offcuts.
- Pricing: Enter a price per piece and/or a price per BF/m³ to get a quick cost breakdown.
Framing Lumber: Studs & Plates
For stud walls, counts are driven by wall length, stud spacing (e.g., 400 mm / 16 in), and wall height. Corner studs and simple opening rules (doors/windows) are included, plus single or double top plates. You’ll see the number of studs, plate pieces by stock length, and overall volume for ordering.
Boards & Trim: From Linear Run to Pieces
Enter a total linear run and select the sizes and stock lengths you plan to purchase. The tool converts to pieces, estimates offcuts, and reports board feet/m³. This is ideal for skirting, fascia, picture rails, handrails, and general trim.
Sheet Goods: Plywood & OSB
Provide the area length and width and pick a standard sheet size (e.g., 1220×2440 mm or 4×8 ft). The calculator returns sheet counts and total coverage with your waste allowance, perfect for floors, walls, and roofs.
Related Project Calculators
- Plywood Calculator – plan sheet counts and coverage precisely.
- Deck Calculator – estimate joists, decking boards, and hardware.
- Drywall Calculator – get sheet, screw, and compound estimates.
FAQs
What’s the difference between nominal and actual lumber size?
Nominal sizes (like 2×4) are the rough-cut names. Actual sizes are smaller after drying/planing (e.g., 1½″×3½″). The calculator uses actual dimensions for accurate volume.
How much waste should I allow?
10% is a sensible default for most jobs. Complex cuts, lots of angles, or premium clear stock may warrant more.
Can I price by board foot or by m³?
Yes. Enter a price per BF (imperial) or per m³ (metric). If you also enter a price per piece, you’ll see both estimates for comparison.
Estimates only. Always check local codes, supplier availability, and on-site conditions before ordering.
Important Estimate Disclaimer
The results provided by this calculator are intended as general estimates only and should not be considered precise engineering measurements. Actual material requirements, costs, and quantities can vary significantly based on site conditions, local building codes, soil type, reinforcement requirements, climate exposure, and the intended use of your project.
These calculators are designed to help you plan and budget your project more effectively, but they do not replace professional advice from a qualified contractor, engineer, or building inspector. Always verify your calculations and assumptions with trained professionals before placing material orders or commencing construction.
For more information on the assumptions, formulas, and data used in these tools, see our Data Sources and Methodology pages.
Material estimates, cost figures, and volume calculations are approximate and may not reflect your actual requirements. Always double-check dimensions and project-specific needs, and consider adding a contingency allowance for waste, over-excavation, and unforeseen conditions.
If you are unsure about any aspect of your project — including structural requirements, reinforcement needs, drainage, or load-bearing capacity — consult with a licensed professional before proceeding.