Dimensional Lumber Calculator

Look up actual vs nominal lumber sizes for all common dimensions. See real measurements for 2×4, 2×6, 4×4, and more.

📏 Dimensional Lumber Calculator

Results

Nominal Size2 × 4 in
Actual Size1.5 × 3.5 in
Cross-Section Area5.25 sq in
Board Feet Each5.33 BF
Total Board Feet5.3 BF

💡 Actual vs. Nominal Lumber Dimensions

Nominal lumber dimensions are not the actual size. A '2×4' is actually 1.5 × 3.5 inches after kiln-drying and planing. This difference matters for precise fitting, calculating board footage, and ordering materials. The larger the nominal size, the greater the dimensional difference.

For 1-inch nominal thickness, actual is 3/4 inch. For 2-inch nominal, actual is 1.5 inches. Widths follow a similar pattern: nominal 4 = 3.5 actual, nominal 6 = 5.5, nominal 8 = 7.25, nominal 10 = 9.25, nominal 12 = 11.25. Posts (4×4) are 3.5 × 3.5 inches, and 6×6 is 5.5 × 5.5.

A nominal 2×4 is actually 1.5 × 3.5 inches — that's a 37% reduction in cross-section area compared to a true 2×4 (5.25 sq in vs 8 sq in).

Dimensional Lumber Calculator FAQ

🔗 Related Calculators

Lumber CalculatorCalculate board feet, weight, and cost for any lumber purchase. Choose from 11 wood species with density data and 8 dimensional lumber presets.Board Foot CalculatorConvert lumber dimensions to board feet for pricing and ordering. Enter thickness, width, length, and quantity.Plywood CalculatorCalculate plywood sheets needed for floors, walls, roofs, or cabinets. Choose from 6 plywood types, 5 thicknesses, and get weight and cost estimates.Square Footage CalculatorCalculate the square footage of any space — rectangle, triangle, circle, trapezoid, or rectangular border. Convert to sq m, sq yd, and acres. Estimate project cost with price per sq ft.