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Nominal vs Actual Lumber Sizes: Lumber Size Chart

By Builders-Tools · Updated · How we calculate

A 2x4 is not 2 in by 4 in. The name is the rough size; the board is dried and planed smaller.

Dimension lumber (dry)

Nominal Actual
2 x 2 1-1/2 x 1-1/2 in
2 x 4 1-1/2 x 3-1/2 in
2 x 6 1-1/2 x 5-1/2 in
2 x 8 1-1/2 x 7-1/4 in
2 x 10 1-1/2 x 9-1/4 in
2 x 12 1-1/2 x 11-1/4 in
4 x 4 3-1/2 x 3-1/2 in
6 x 6 5-1/2 x 5-1/2 in

Boards

A 1x4 is 3/4 x 3-1/2 in, a 1x6 is 3/4 x 5-1/2 in and a 1x8 is 3/4 x 7-1/4 in.

Why

The American Softwood Lumber Standard (PS 20) sets minimum dressed sizes. Lumber surfaced green is cut a little bigger, because it shrinks as it dries.

Board feet are figured on the nominal size: see the board foot calculator.

Sources

Sources last checked 1 November 2026.

Frequently asked questions

How big is a 2x4 really?

1-1/2 x 3-1/2 in.

How wide is a 2x6?

5-1/2 in.

Why are lumber sizes smaller than the name?

Lumber is named by its rough size, then dried and planed to the dressed size in PS 20.

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