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Lumber Dimensions: Nominal vs. Actual

Lumber sizes can be confusing at first. Boards are referred to by their "Nominal Size", not the actual size. This is because lumber is surfaced or planed smooth on four sides (S4S). The nominal measurement is made before the lumber is surfaced.  Always check your lumber when precise measurements are needed.

Nominal SizeActual Size
1x23/4" x 1-1/2"
1x33/4" x 2-1/2"
1x43/4" x 3-1/2"
1x63/4" x 5-1/2"
1x83/4" x 7-1/4"
1x103/4" x 9-1/4"
1x123/4" x 11-1/4"
2x21-1/2" x 1-1/2"
2x31-1/2" x 2-1/2"
2x41-1/2" x 3-1/2"
2x61-1/2" x 5-1/2"
2x81-1/2" x 7-1/4"
2x101-1/2" x 9-1/4"
2x121-1/2" x 11-1/4"
4x43-1/2" x 3-1/2"
4x63-1/2" x 5-1/2"
6x65-1/2" x 5-1/2"

Decking Planks

Nominal SizeActual Size
5/4 x 61" x 5-1/2"
6/4 x 61-5/16" x 5-1/2"
Sutherlands® provides these project tips and guides as a service to our visitors. Due to possible variance in conditions, equipment, materials and individual skill levels, Sutherlands® assumes no responsibility for losses or injuries incurred during maintenance or repair of your property. Sutherlands® assumes no liability for errors or omissions in the Resources section of this website. Please read and follow any safety precautions provided by tool and equipment manufacturers, and consult a building professional in your area if you have any questions about a repair project. Always check your local codes before building, and obtain the required building permits.