Common Lumber: Nominal vs. Actual Dimensions
| Nominal Size | Actual Size (inches) |
|---|---|
| 1 × 2 | 0.75 × 1.5 |
| 1 × 4 | 0.75 × 3.5 |
| 1 × 6 | 0.75 × 5.5 |
| 2 × 4 | 1.5 × 3.5 |
| 2 × 6 | 1.5 × 5.5 |
| 2 × 8 | 1.5 × 7.25 |
| 2 × 10 | 1.5 × 9.25 |
| 2 × 12 | 1.5 × 11.25 |
| 4 × 4 | 3.5 × 3.5 |
About the Board Foot Calculator
A board foot is the standard unit of measurement for hardwood lumber in North America. One board foot equals a piece of wood 1 inch thick, 12 inches wide, and 12 inches long (144 cubic inches). Hardwood dealers, sawmills, and specialty lumber yards price their stock by the board foot, making this calculation essential for accurate project budgeting.
When calculating board feet, the dimensions you enter depend on the type of lumber. For softwood construction lumber (2x4, 2x6, etc. from home improvement stores), use nominal dimensions — a "2x6" is entered as 2" thick and 6" wide, even though the actual size is 1.5" x 5.5". For hardwood lumber from lumber dealers, use the actual rough thickness based on the quarter system: 4/4 = 1", 5/4 = 1.25", 6/4 = 1.5", 8/4 = 2". Hardwood widths and lengths are measured as actual dimensions. The reference table above shows common softwood nominal-to-actual conversions.
For project planning, add 10-15% to your calculated board footage to account for waste from defects, saw kerf, and layout inefficiency. This is especially important when working with rough-sawn lumber that needs to be planed and jointed to final dimensions, as each pass removes material from your purchased volume.