Convertisseur de dimensions du bois

The Lumber Dimension Converter handles the confusing reality that lumber labeled '2×4' is not actually 2 inches × 4 inches — the actual dimensions are 1.5 × 3.5 inches. This nominal vs actual difference (a residual of historical milling practices before kiln drying became standard) catches every beginner woodworker and DIYer. The calculator converts nominal sizes (1×2 through 6×6) to actual inches and millimeters, calculates board feet (BF, the standard lumber volume unit), converts length units (feet, inches, meters, centimeters), and computes total project costs based on price per board foot. The nominal-vs-actual lumber sizing system originated in the early 1900s when rough-sawn green wood was sold at its true dimensions. As kiln drying and finish planing became standard processes through the 1920s-1950s, wood shrunk during drying and lost dimension during planing — but the industry kept the original 'nominal' name for tradition, supply chain consistency, and marketing simplicity. A 2×4 was always called a 2×4 even after milling reduced it to 1.5×3.5 inches. The American Softwood Lumber Standard PS 20 formalizes these nominal vs actual relationships used across North American construction. Board feet (BF) is the standard volume unit in North American lumber commerce. One board foot equals 144 cubic inches (12″×12″×1″) or about 0.00236 cubic meters. Critically, board feet calculation uses NOMINAL dimensions, not actual — this is the convention regardless of physical accuracy. A 2×4×8 piece equals (2×4×8)/12 = 5.33 board feet, even though its actual volume is only (1.5×3.5×96)/144 ≈ 3.5 BF. This convention persists because traditional sawmill output and pricing has been based on nominal volumes since the 1800s. This calculator handles the practical reality of buying and building with lumber. Select nominal size from 17 common sizes (1×2 through 6×6), enter length and unit, quantity, and optional price per board foot. The calculator outputs total board feet, actual dimensions in inches and millimeters, length converted across all common units, and total cost. Use for: woodworking project planning, construction estimation, comparing pricing across retailers (always in board feet), and understanding what lumber will actually fit your design constraints.

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1. 1Step 1 — Select Nominal Lumber Size: Choose from dropdown of 17 common North American softwood lumber sizes: 1×2, 1×3, 1×4, 1×6, 1×8, 1×10, 1×12 (1-inch nominal thickness boards) and 2×2, 2×3, 2×4 (most common), 2×6, 2×8, 2×10, 2×12 (2-inch nominal framing lumber) plus 4×4, 4×6, 6×6 (timber/posts).
2. 2Step 2 — Enter Length and Unit: Lumber length comes in standard 8, 10, 12, 14, 16 foot lengths (sometimes 6 or 20 foot). Enter your needed length and select unit. Calculator converts feet, inches, meters, or centimeters internally to feet for board feet calculation.
3. 3Step 3 — Enter Quantity: How many pieces you need. Quantity is multiplied for total board feet and total cost.
4. 4Step 4 — Enter Price per Board Foot: Optional but useful. Standard 2×4 SPF pine: $3-5/BF. Premium hardwood (oak, maple): $5-15/BF. Exotic hardwood (walnut, cherry): $10-30/BF. Reclaimed lumber: $4-12/BF. Check current local pricing.
5. 5Step 5 — Calculator Outputs Board Feet: Board Feet per piece = (Nominal Thickness × Nominal Width × Length in feet) ÷ 12. For 2×4×8: (2×4×8)/12 = 5.33 BF. Total BF = per piece × quantity.
6. 6Step 6 — Review Actual Dimensions: Calculator displays actual inches and actual millimeters. Critical for joinery planning — your 'two-by-four' shelf bracket actually needs to clear 1.5×3.5″ structural members, not 2×4.
7. 7Step 7 — Total Cost Calculation: If price per BF entered, total cost = Total BF × Price/BF. Use for comparing retailers — always compare price per BF since lumber pricing varies by length, grade, and species.

• !Calculating board feet using actual dimensions — must use nominal per industry convention.
• !Assuming 2×4 = 2 inches × 4 inches — it's 1.5 × 3.5 inches actual; design around actual.
• !Forgetting drying causes additional shrinkage — kiln-dried is more dimensionally accurate than green lumber.
• !Mixing hardwood (often sold by exact dimensions) and softwood (sold by nominal) measurement systems.
• !Buying nominal-stated lengths exactly — boards are often slightly longer than stated (8' actually 96.5"+) to allow trimming ends.