Lumber Dimensions Reference Chart

Understanding nominal vs. actual lumber dimensions saves time on every cut and estimate. "Nominal" is the name lumberyards use; "actual" is what you receive.

Dimensional Lumber (Softwood)

Nominal	Actual (in)	Actual (mm)
1x2	0.75 x 1.5	19 x 38
1x3	0.75 x 2.5	19 x 64
1x4	0.75 x 3.5	19 x 89
1x6	0.75 x 5.5	19 x 140
1x8	0.75 x 7.25	19 x 184
1x10	0.75 x 9.25	19 x 235
1x12	0.75 x 11.25	19 x 286
2x2	1.5 x 1.5	38 x 38
2x3	1.5 x 2.5	38 x 64
2x4	1.5 x 3.5	38 x 89
2x6	1.5 x 5.5	38 x 140
2x8	1.5 x 7.25	38 x 184
2x10	1.5 x 9.25	38 x 235
2x12	1.5 x 11.25	38 x 286
4x4	3.5 x 3.5	89 x 89
4x6	3.5 x 5.5	89 x 140

Why the Difference?

Lumber is sized when green (wet) and shrinks during kiln-drying. The industry standardized on today's actual sizes around 1964. When you calculate board feet or plan joinery, always use actual dimensions.

Plywood Sizes

Standard plywood sheets are nominally 4 x 8 ft (actual: 48 x 96 in). Thickness is also nominal:

Nominal	Actual (in)
1/4"	0.234
3/8"	0.359
1/2"	0.469
5/8"	0.594
3/4"	0.719

Tip: When routing dadoes or rabbets for plywood panels, measure the actual sheet, not the nominal thickness.