The actual size of 2×12 lumber is 1 1/2 x 11 1/4 inches (38 x 286 mm). Even though the nominal size is less than the actual size, it is still called 2-by-12 lumber. Originally the board was of the exact measurements, but in hardware stores it’s planned from all four sides, resulting in a reduction in thickness.
- Nominal size: It’s the measurement of lumber to indicate the dimensions of wood lumber before it gets planned from all sides.
- Actual size: A board’s actual size is determined by its measurement after it has been planned.
Hence, their sizes differ. To ensure that your project gets the exact 2×12 lumber you need, measure it carefully since 2×12 lumbers at hardware stores are usually a little smaller than they advertise.
2×12 lumber Length
Regardless of the nominal or actual length of a 2×12 board, it remains the same.
For example,
- Considering the nominal length of 2×12 to be 6 feet, the actual length will also be 6 feet.
- The actual length will also be 8 feet if the nominal length is 8.
- A nominally lengthened board of 12 feet will actually measure 12 feet long.
2×12 lumber dimensions
| 2×12 lumber | Nominal size in inches | Actual size in inches |
| 2 | 1 ½ | |
| 12 length | 11 1/4 inches |
| 2×12 Lumber | Nominal size in mm | Actual size in mm |
| 50.8 | 38 | |
| 304.8 | 286 |
Why is the actual size of a 2×12 lumber smaller than its nominal size?
Plans are generally measured in their original shape when they are rough-sawn. To make planks, the boards are treated and planed.
Planning creates a uniform thickness by smoothing the surface of the timber. The thickness of a timber shrinks as thin layers are sliced off as a result of planning through each side of the timber. This way, timbers with 4-sided smooth surfaces generally lose thickness and width, reducing their actual dimensions.
