Ed Mauro

Nominal Dimensions

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by

Ed
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When most people think of something like a 2×4, they think its measurements would be 2 inches by 4 inches, right? Well, not quite… they do start out that way but by the time they get cleaned up for sale they’re smaller. A 2×4 is actually 1-1/2 by 3-1/2. It takes some getting used to. Here are some common “nominal” dimensions and their actual sizes.

North American 1-by Lumber

Nominal SizeActual Size (inches)Actual Size (mm)
1×2″3/4 x 1-1/2″19 x 38
1×3″3/4 x 2-1/2″19 x 64
1×4″3/4 x 3-1/2″19 x 89
1×6″3/4 x 5-1/2″19 x 140
1×8″3/4 x 7-1/4″19 x 184
1×10″3/4 x 9-1/4″19 x 235
1×12″3/4 x 11-1/4″19 x 286

North American 2-by Lumber

Nominal SizeActual Size (inches)Actual Size (mm)
2×2″1-1/2 x 1-1/238 x 38
2×3″1-1/2 x 2-1/238 x 64
2×4″1-1/2 x 3-1/238 x 89
2×6″1-1/2 x 5-1/238 x 140
2×8″1-1/2 x 7-1/438 x 184
2×10″1-1/2 x 9-1/438 x 235
2×12″1-1/2 x 11-1/438 x 286

North American 4-by Lumber

Nominal SizeActual Size (inches)Actual Size (mm)
4×4″3-1/2 x 3-1/2″89 x 89
4×6″3-1/2 x 5-1/2″89 x 140
4×8″3-1/2 x 7-1/4″89 x 184
4×10″3-1/2 x 9-1/4″89 x 235
4×12″3-1/2 x 11-1/4″89 x 286