Construction · lumber
Nominal vs actual lumber size chart.
A 2x4 is 1-1/2 by 3-1/2 inches. See the real size of every 2-inch framing board, the cross-section it keeps, and its board feet by nominal and actual size.
Board
Result
Chart: 2-inch framing lumber, dry surfaced
| Nominal (in.) | Actual (in.) | Actual cross-section (sq in.) |
|---|---|---|
| 2 x 4 | 1-1/2 x 3-1/2 | 5.25 |
| 2 x 6 | 1-1/2 x 5-1/2 | 8.25 |
| 2 x 8 | 1-1/2 x 7-1/4 | 10.875 |
| 2 x 10 | 1-1/2 x 9-1/4 | 13.875 |
| 2 x 12 | 1-1/2 x 11-1/4 | 16.875 |
Worked example
A nominal 2x6 is 1-1/2 x 5-1/2 in., a cross-section of 8.25 sq in. against the 12 sq in. its name suggests, or 68.8%. Twelve feet of it is 12 board feet on the nominal basis (2 x 6 x 12 / 12), which is the example Penn State Extension uses, but only 8.25 board feet if you measured the actual size. Ten 8 ft 2x4s are 53.3 board feet nominal.
Method and sources
Sizes: the actual surfaced sizes come from the American Wood Council Span Tables for Joists and Rafters, Explanation of Tables item 3 (Lumber Sizes) (2023; retrieved 2026-10), which states that the tabulated sizes conform to the American Softwood Lumber Standard, PS 20-20, and are dry sizes at 19 percent maximum moisture content: 2x4 = 1-1/2 x 3-1/2, 2x6 = 1-1/2 x 5-1/2, 2x8 = 1-1/2 x 7-1/4, 2x10 = 1-1/2 x 9-1/4, 2x12 = 1-1/2 x 11-1/4 in. Board feet = thickness (in.) × width (in.) × length (ft) / 12, where one board foot is 144 cubic inches (Penn State Extension, Missouri Extension G5050). The nominal-basis figure follows Penn State’s worked example of a 12 ft 2-by-6 as 12 board feet; whether a seller prices on nominal or actual size is the seller’s convention, so ask. Limits: only 2-inch dry framing lumber is tabulated here. Boards (1x), 4x and larger timbers, green or rough lumber and metric-sized lumber have different dimensions and are not shown.
FAQ
What is the actual size of a 2x4?
1-1/2 by 3-1/2 inches for dry surfaced lumber under the American Softwood Lumber Standard, PS 20-20 (AWC Span Tables for Joists and Rafters).
What are the actual sizes of 2x6, 2x8, 2x10 and 2x12?
2x6 is 1-1/2 x 5-1/2, 2x8 is 1-1/2 x 7-1/4, 2x10 is 1-1/2 x 9-1/4 and 2x12 is 1-1/2 x 11-1/4 inches.
Are board feet figured on nominal or actual size?
Penn State Extension’s worked example treats a 12 ft 2-by-6 as 12 board feet, which is the nominal calculation. Pricing conventions vary by seller, so confirm which basis the quote uses. The tool shows both.
Does this chart cover 1x boards and 4x4 posts?
No. The source tabulates 2-inch framing lumber, and this chart does not guess at other sizes.