Complete reference chart for standard lumber sizes. Nominal dimensions are what's on the label — actual dimensions are what you measure. Use this chart to plan cuts, estimate materials, and avoid costly mistakes.
Lumber is named by its rough-cut size before kiln-drying and planing. Drying shrinks the wood, planing smooths all four sides, and the result is a board smaller than its name suggests. A 2×4 starts at 2″×4″ but finishes at 1½″×3½″.
Weights based on kiln-dried Douglas Fir (approximately 30 lbs/ft³). Board feet calculated using nominal dimensions per standard industry practice.
| Nominal Size | Actual (in) | Actual (mm) | Wt/ft (lbs) | BF/ft |
|---|---|---|---|---|
| 1 × 2 | ¾ × 1½ | 19 × 38 | 0.17 | 0.17 |
| 1 × 3 | ¾ × 2½ | 19 × 64 | 0.28 | 0.25 |
| 1 × 4 | ¾ × 3½ | 19 × 89 | 0.39 | 0.33 |
| 1 × 6 | ¾ × 5½ | 19 × 140 | 0.62 | 0.50 |
| 1 × 8 | ¾ × 7¼ | 19 × 184 | 0.81 | 0.67 |
| 1 × 10 | ¾ × 9¼ | 19 × 235 | 1.04 | 0.83 |
| 1 × 12 | ¾ × 11¼ | 19 × 286 | 1.26 | 1.00 |
| Nominal Size | Actual (in) | Actual (mm) | Wt/ft (lbs) | BF/ft |
|---|---|---|---|---|
| 2 × 2 | 1½ × 1½ | 38 × 38 | 0.45 | 0.33 |
| 2 × 3 | 1½ × 2½ | 38 × 64 | 0.75 | 0.50 |
| 2 × 4 | 1½ × 3½ | 38 × 89 | 1.05 | 0.67 |
| 2 × 6 | 1½ × 5½ | 38 × 140 | 1.65 | 1.00 |
| 2 × 8 | 1½ × 7¼ | 38 × 184 | 2.18 | 1.33 |
| 2 × 10 | 1½ × 9¼ | 38 × 235 | 2.77 | 1.67 |
| 2 × 12 | 1½ × 11¼ | 38 × 286 | 3.37 | 2.00 |
| Nominal Size | Actual (in) | Actual (mm) | Wt/ft (lbs) | BF/ft |
|---|---|---|---|---|
| 4 × 4 | 3½ × 3½ | 89 × 89 | 2.45 | 1.33 |
| 4 × 6 | 3½ × 5½ | 89 × 140 | 3.85 | 2.00 |
| 4 × 8 | 3½ × 7¼ | 89 × 184 | 5.08 | 2.67 |
| 4 × 10 | 3½ × 9¼ | 89 × 235 | 6.47 | 3.33 |
| 4 × 12 | 3½ × 11¼ | 89 × 286 | 7.87 | 4.00 |
| 6 × 6 | 5½ × 5½ | 140 × 140 | 6.05 | 3.00 |
| 6 × 8 | 5½ × 7½ | 140 × 190 | 8.25 | 4.00 |
| 6 × 10 | 5½ × 9½ | 140 × 241 | 10.45 | 5.00 |
| 6 × 12 | 5½ × 11½ | 140 × 292 | 12.66 | 6.00 |
Lumber comes in standard lengths from 6 to 24 feet in 2-foot increments: 6, 8, 10, 12, 14, 16, 18, 20, 22, and 24 feet. Unlike width and thickness, length is actual — an 8-foot board is truly 96 inches.
Stud-grade lumber also comes in precut lengths: 92⅝″ for 8-foot walls and 104⅝″ for 9-foot walls, sized to account for top and bottom plates so the finished wall height comes out right.
A quick mental shortcut for estimating actual dimensions:
| Nominal Thickness | Subtract from Each Dimension |
|---|---|
| Under 2″ (1× boards) | ¼″ from each dimension |
| 2″ to 6″ nominal | ½″ from each dimension |
| 8″ and wider | ¾″ from width (thickness still subtracts ½″) |
| Size | Common Uses |
|---|---|
| 1×4, 1×6 | Trim, shelving, fence boards, furring strips |
| 2×4 | Wall framing, ceiling joists, light-duty projects |
| 2×6 | Exterior wall framing, floor joists (short spans), deck boards |
| 2×8 | Floor joists, headers, rafters |
| 2×10 | Floor joists (longer spans), stair stringers, headers |
| 2×12 | Ridge boards, large headers, stair stringers |
| 4×4 | Fence posts, deck posts, structural columns |
| 6×6 | Heavy-duty posts, beams, pergola columns |
This chart covers softwood dimensional lumber (pine, spruce, fir, cedar). It does not apply to:
Need to calculate board feet for pricing? Use our Board Foot Calculator.
Lumber is named by its rough-cut size before processing. After kiln-drying and planing smooth on all four sides, a 2×4 finishes at 1½ × 3½ inches. This naming convention has been the industry standard for over a century.
No. An 8-foot board is truly 8 feet (96 inches). The nominal vs actual difference only applies to thickness and width. Lengthwise shrinkage during drying is negligible.
Yes. Both countries follow the same standards set by the American Lumber Standard Committee (PS 20). A 2×4 is 1½ × 3½ inches on both sides of the border.
A kiln-dried Douglas Fir or Southern Pine 2×4 weighs roughly 1.0–1.1 pounds per linear foot. An 8-foot stud weighs about 8–9 pounds. Green (wet) lumber can weigh nearly twice as much.
Standard interior walls use 2×4s at 16 inches on center. Exterior walls and walls requiring more insulation use 2×6s. Floor joists are typically 2×8, 2×10, or 2×12 depending on the span. Check local building codes for your specific application.
Always order by nominal size — that's what stores, suppliers, and building plans use. When planning your project layout and cuts, work with the actual dimensions so everything fits correctly.