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Woodworking Math

1x6 actual size

Dry (19% moisture or less)

3/4 × 5-1/2 in

19.1 × 139.7 mm

From the standard, NIST PS 20-25

End view to scale: dashed is the nominal 1x6, filled is the dry dressed size.

Nominal, dry and green

SizeThicknessWidth
Nominal (the name)1 in6 in
Dry, minimum3/4 in (19.1 mm)5-1/2 in (139.7 mm)
Green, minimum13/16 in (19.8 mm)5-5/8 in (142.9 mm)

A 1x6 is boards (under 2 in nominal thickness) under the American Softwood Lumber Standard, NIST PS 20-25. The standard names lumber by its nominal size and sets the smallest it may be once it has been dressed (planed smooth). Lumber dried to 19% moisture content or less is held to the dry size; lumber surfaced green, above 19%, is left a little bigger because it shrinks as it dries.

Board feet in a 1x6

Thickness × width ÷ 12 gives the board feet in each foot of length. By the nominal size that is 0.5 bd ft per foot; by the dry dressed size it is 0.344. Ask your yard which one it prices on.

LengthNominal bd ftActual (dry) bd ft
8 ft42.75
10 ft53.44
12 ft64.13
16 ft85.5

For a whole order, use the board foot calculator. Every size side by side is on the lumber sizes chart.

Sources

  1. NIST (US Department of Commerce), Voluntary Product Standard PS 20-25, American Softwood Lumber Standard, Table 3 (effective January 2025), read 2026-11-07
  2. Engineering ToolBox, Softwood lumber: nominal and actual (dry) sizes, read 2026-11-07
  3. WoodBin, Standard dimensions of lumber (hardwood thickness after G. Wengert; softwood dry and green sizes), read 2026-11-07

How we source these numbers