Tuesday, September 26, 2017

Wood Sizes - Q. When is a 2x4 not a 2x4?

A. All the time in the USA

Have you ever got upset if you get home after a morning shopping in Home Depot (or any other hardware store), only to discover that the wood you bought is not what you thought?  The dimensions marked are NOMINAL.  Their actual dimensions can vary.  They are always less and usually about the values in the following tables.  Why?, because NIST (National Institute of Standards) says so.  It probably came about because lumber was originally sized by it's rough sawn dimensions (straight from the mill), but then for most applications it needed to be straightened and smoothed (called dressing).  Obviously that lost a bit and NIST stepped in to define how much it was allowed to be reduced and still be called a 2x4.

You can study the following tables and commit it to heart.  Or you can download the definitive doc. But honestly there is a much easier way.  For MOST lumber just:

Subtract 1/4" for anything 1" nominal,Subtract 1/2" from any dimension over 1" but under 8"Subtract 3/4" for anything 8" nominal and over.

Softwood Lumber Dimensions
NOMINAL SIZE (INCHES)
ACTUAL SIZE (INCHES)
ACTUAL SIZE (MM)
1 x 2
3/4 x 1 1/2
19 x 38
1 x 3
3/4 x 2 1/2
19 x 64
1 x 4
3/4 x 3 1/2
19 x 89
1 x 6
3/4 x 5 1/2
19 x 140
1 x 8
3/4 x 7 1/4
19 x 184
1 x 10
3/4 x 9 1/4
19 x 235
1 x 12
3/4 x 11 1/4
19 x 286
NOMINAL SIZE (INCHES)
ACTUAL SIZE (INCHES)
ACTUAL SIZE (MM)
2 x 2
1 1/2 x 1 1/2
38 x 38
2 x 3
1 1/2 x 2 1/2
38 x 64
2 x 4
1 1/2 x 3 1/2
38 x 89
2 x 6
1 1/2 x 5 1/2
38 x 140
2 x 8
1 1/2 x 7 1/4
38 x 184
2 x 10
1 1/2 x 9 1/4
38 x 235
2 x 12
1 1/2 x 11 1/4
38 x 286
NOMINAL SIZE (INCHES)
ACTUAL SIZE (INCHES)
ACTUAL SIZE (MM)
3 x 3
2 1/2 x 2 1/2
64 x 64
3 x 4
2 1/2 x 3 1/2
64 x 89
3 x 6
2 1/2 x 5 1/2
64 x 140
3 x 8
2 1/2 x 7 1/4
64 x 184
3 x 10
2 1/2 x 9 1/4
64 x 235
3 x 12
2 1/2 x 11 1/4
64 x 286
NOMINAL SIZE (INCHES)
ACTUAL SIZE (INCHES)
ACTUAL SIZE (MM)
4 x 4
3 1/2 x 3 1/2
89 x 89
4 x 6
3 1/2 x 5 1/2
89 x 140
4 x 8
3 1/2 x 7 1/4
89 x 184
4 x 10
3 1/2 x 9 1/4
89 x 235
4 x 12
3 1/2 x 11 1/4
89 x 286
NOMINAL SIZE (INCHES)
ACTUAL SIZE (INCHES)
ACTUAL SIZE (MM)
6 x 6
5 1/2 x 5 1/2
140 x 140
NOMINAL SIZE (INCHES)
ACTUAL SIZE (INCHES)
ACTUAL SIZE (MM)
8 x 8
7 1/4 x 7 1/4
184 x 184


LENGTH IN FEET
LENGTH IN INCHES
LENGTH IN METERS
6 feet
72 inches
1.829 meters
8 feet
96 inches
2.438 meters
10 feet
120 inches
3.048 meters
12 feet
144 inches
3.658 meters
14 feet
168 inches
4.267 meters
16 feet
192 inches
4.877 meters
18 feet
216 inches
5.486 meters
20 feet
240 inches
6.096 meters
22 feet
264 inches
6.706 meters
24 feet
288 inches
7.315 meters

Hardwood Lumber Dimensions
Hardwood lumber is sized based on how many sides are surfaced. Surfaced refers to a finishing process that smooths the lumber to remove all saw marks.

In North America, hardwood lumber is usually specified using the quarter system, where a board is identified by its thickness in quarters of an inch. For instance, hardwood trim that ends up being just over 1" thick (surfaced on 2 sides) is called a five-quarter (5/4) board.

Hardwood board widths vary. In most cases, hardwood boards come in random widths to be ripped to size by the woodworker. However, in some cases, like the big-box hardware stores, the boards come in dimensional widths similar to softwood widths. 

NOMINAL SIZE
ROUGH SIZE
ACTUAL: SURFACED 1 SIDE
ACTUAL: SURFACED 2 SIDES

1/2 inch
3/8 inch (9.5 mm)
5/16 inch (7.9 mm)

5/8 inch
1/2 inch (13 mm)
7/16 inch (11 mm)

3/4 inch
5/8 inch (16 mm)
9/16 inch (14 mm)
4/4 inch
1 inch
7/8 inch (22 mm)
13/16 inch (21 mm)
5/4 inch
1 1/4 inch
1 1/8 inch (29 mm)
1 1/16 inch (27 mm)
6/4 inch
1 1/2 inch
1 3/8 inch (35 mm)
1 5/16 inch (33 mm)
8/4 inch
2 inches
1 13/16 inch (46 mm)
1 3/4 inch (44 mm)
12/4 inch
3 inches
2 13/16 inch (71 mm)
2 3/4 inch (70 mm)
16/4 inch
4 inches
3 13/16 inch (97 mm)
3 3/4 inch (95 mm)


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