Lumber Size Guide
Nominal sizes are what the store sells. Actual sizes are what you really get.
Kiln-dried dimensional lumber. Width listed first, thickness second.
1×2
actual size
3/4" × 1-1/2"
1×3
actual size
3/4" × 2-1/2"
1×4
Common for trim & accent walls
actual size
3/4" × 3-1/2"
1×6
Common for shiplap & boards
actual size
3/4" × 5-1/2"
1×8
actual size
3/4" × 7-1/4"
1×10
actual size
3/4" × 9-1/4"
1×12
actual size
3/4" × 11-1/4"
2×2
actual size
1-1/2" × 1-1/2"
2×3
actual size
1-1/2" × 2-1/2"
2×4
Most common framing lumber
actual size
1-1/2" × 3-1/2"
2×6
Wall framing & shelving
actual size
1-1/2" × 5-1/2"
2×8
actual size
1-1/2" × 7-1/4"
2×10
actual size
1-1/2" × 9-1/4"
2×12
actual size
1-1/2" × 11-1/4"
4×4
Posts & fence
actual size
3-1/2" × 3-1/2"
4×6
actual size
3-1/2" × 5-1/2"
4×8
actual size
3-1/2" × 7-1/2"
6×6
Heavy posts & beams
actual size
5-1/2" × 5-1/2"
6×8
actual size
5-1/2" × 7-1/2"
8×8
actual size
7-1/2" × 7-1/2"
Why the difference?
Lumber is cut to nominal size when green and wet, then dried and planed smooth — which removes material. The nominal name stuck even though the actual size shrank. Always use actual dimensions when planning cuts and spacing.