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Understanding Lumber Dimensions
One of the most common sources of confusion when working with lumber is the difference between nominal and actual dimensions. When you purchase a "2x4," you are not getting a board that is 2 inches by 4 inches. The nominal size refers to the rough-sawn dimension before the wood is dried and planed smooth. After drying and surfacing, the actual dimensions are smaller.
With reclaimed lumber, dimensions can vary even further. Older lumber was often cut to true dimensions or milled to slightly different standards than modern lumber. A reclaimed 2x4 from a 100-year-old barn may actually be closer to 2" x 4" than a modern one. This is one reason reclaimed lumber is prized: thicker, denser boards with tighter grain from old-growth timber that is no longer available from modern mills.
Below you will find detailed reference tables for every common lumber dimension, board foot calculations, engineered lumber sizes, decking and timber frame dimensions, weight-per-board-foot by species, coverage estimators for different applications, and more. Visit our yard at 37 Linden St, Medford, MA 02155 to measure and inspect reclaimed stock in person.
Nominal vs. Actual Dimensions
Softwood lumber (pine, spruce, fir, cedar) after kiln drying and surfacing
| Nominal Size (in) | Actual Size (in) | Actual Size (mm) | Difference (in) | Common Uses |
|---|---|---|---|---|
| 1 x 2 | 3/4 x 1-1/2 | 19 x 38 | 1/4 x 1/2 | Furring strips, shims, craft projects |
| 1 x 3 | 3/4 x 2-1/2 | 19 x 64 | 1/4 x 1/2 | Lattice, trim, small shelving |
| 1 x 4 | 3/4 x 3-1/2 | 19 x 89 | 1/4 x 1/2 | Trim, shelving, fence pickets |
| 1 x 6 | 3/4 x 5-1/2 | 19 x 140 | 1/4 x 1/2 | Shelving, siding, fence boards |
| 1 x 8 | 3/4 x 7-1/4 | 19 x 184 | 1/4 x 3/4 | Shelving, sheathing, wainscoting |
| 1 x 10 | 3/4 x 9-1/4 | 19 x 235 | 1/4 x 3/4 | Wide shelves, tabletops, paneling |
| 1 x 12 | 3/4 x 11-1/4 | 19 x 286 | 1/4 x 3/4 | Wide shelving, cabinet sides |
| 2 x 2 | 1-1/2 x 1-1/2 | 38 x 38 | 1/2 x 1/2 | Furring, stakes, balusters |
| 2 x 3 | 1-1/2 x 2-1/2 | 38 x 64 | 1/2 x 1/2 | Light framing, furring |
| 2 x 4 | 1-1/2 x 3-1/2 | 38 x 89 | 1/2 x 1/2 | Wall framing, general construction |
| 2 x 6 | 1-1/2 x 5-1/2 | 38 x 140 | 1/2 x 1/2 | Floor joists, wall framing, decking |
| 2 x 8 | 1-1/2 x 7-1/4 | 38 x 184 | 1/2 x 3/4 | Floor joists, rafters, headers |
| 2 x 10 | 1-1/2 x 9-1/4 | 38 x 235 | 1/2 x 3/4 | Floor joists, headers, beams |
| 2 x 12 | 1-1/2 x 11-1/4 | 38 x 286 | 1/2 x 3/4 | Joists, rafters, stair stringers |
| 4 x 4 | 3-1/2 x 3-1/2 | 89 x 89 | 1/2 x 1/2 | Posts, columns, porch railings |
| 4 x 6 | 3-1/2 x 5-1/2 | 89 x 140 | 1/2 x 1/2 | Posts, beams, heavy framing |
| 6 x 6 | 5-1/2 x 5-1/2 | 140 x 140 | 1/2 x 1/2 | Heavy posts, timber framing |
| 6 x 8 | 5-1/2 x 7-1/2 | 140 x 190 | 1/2 x 1/2 | Beams, timber framing |
| 8 x 8 | 7-1/2 x 7-1/2 | 190 x 190 | 1/2 x 1/2 | Heavy beams, timber framing |
| 8 x 12 | 7-1/2 x 11-1/2 | 190 x 292 | 1/2 x 1/2 | Major structural beams |
| 10 x 10 | 9-1/2 x 9-1/2 | 241 x 241 | 1/2 x 1/2 | Large posts, timber frame bents |
| 12 x 12 | 11-1/2 x 11-1/2 | 292 x 292 | 1/2 x 1/2 | Major timbers, bridge beams |
Note on reclaimed lumber: Reclaimed boards often measure closer to true nominal dimensions because they were milled before modern surfacing standards were adopted. A reclaimed 2x4 might measure 1-3/4" x 3-3/4" or even a full 2" x 4". Always verify dimensions before planning your project. We can custom-mill reclaimed stock to any dimension you need.
Hardwood Lumber Thickness
Hardwood is sold in quarter-inch increments, referred to as "quarter" sizing
| Quarter Designation | Rough Thickness (in) | Surfaced 1 Side (S1S) | Surfaced 2 Sides (S2S) | Metric (mm) Rough | Typical Applications |
|---|---|---|---|---|---|
| 3/4 (Three Quarter) | 3/4" | 5/8" | 9/16" | 19 | Small crafts, thin panels, drawer bottoms |
| 4/4 (Four Quarter) | 1" | 7/8" | 13/16" | 25 | Furniture, cabinetry, general woodworking |
| 5/4 (Five Quarter) | 1-1/4" | 1-1/8" | 1-1/16" | 32 | Tabletops, heavy shelving, decking |
| 6/4 (Six Quarter) | 1-1/2" | 1-3/8" | 1-5/16" | 38 | Table legs, thick shelves, workbenches |
| 7/4 (Seven Quarter) | 1-3/4" | 1-5/8" | 1-9/16" | 44 | Heavy furniture, stair treads |
| 8/4 (Eight Quarter) | 2" | 1-7/8" | 1-13/16" | 51 | Thick tabletops, mantels, bench tops |
| 10/4 (Ten Quarter) | 2-1/2" | 2-3/8" | 2-5/16" | 64 | Turning blanks, heavy beams, sculptures |
| 12/4 (Twelve Quarter) | 3" | 2-7/8" | 2-13/16" | 76 | Carving blanks, large turning, structural |
| 16/4 (Sixteen Quarter) | 4" | 3-7/8" | 3-13/16" | 102 | Heavy timber, posts, large sculptures |
Engineered Lumber Dimensions
Standard sizes for LVL, glulam beams, and I-joists used in modern and hybrid construction
LVL (Laminated Veneer Lumber)
Used for headers, beams, and rim boards
| Width | Common Depths |
|---|---|
| 1-3/4" | 5-1/2", 7-1/4", 9-1/4", 9-1/2", 11-1/4", 11-7/8", 14", 16", 18" |
| 3-1/2" | 5-1/2", 7-1/4", 9-1/4", 11-1/4", 14", 16", 18" |
| 5-1/4" | 7-1/4", 9-1/4", 11-1/4", 14", 16", 18" |
| 7" | 9-1/4", 11-1/4", 14", 16", 18" |
Glulam Beams
Used for exposed beams, posts, and long-span headers
| Width | Common Depths |
|---|---|
| 3-1/8" | 6", 7-1/2", 9", 10-1/2", 12", 13-1/2", 15" |
| 5-1/8" | 6", 7-1/2", 9", 10-1/2", 12", 13-1/2", 15", 16-1/2", 18" |
| 6-3/4" | 9", 10-1/2", 12", 13-1/2", 15", 16-1/2", 18", 19-1/2", 21" |
| 8-3/4" | 12", 13-1/2", 15", 16-1/2", 18", 19-1/2", 21", 22-1/2", 24" |
I-Joists (TJI)
Used for floor and roof framing
| Depth | Flange Width | Max Span (approx.) |
|---|---|---|
| 9-1/2" | 1-3/4" or 2-5/16" | 14-16' |
| 11-7/8" | 1-3/4" or 2-5/16" | 17-20' |
| 14" | 1-3/4" or 2-5/16" | 20-24' |
| 16" | 1-3/4" or 2-5/16" | 24-28' |
| 18" | 2-5/16" or 3-1/2" | 28-32' |
| 20" | 2-5/16" or 3-1/2" | 30-36' |
Decking Dimensions
| Nominal | Actual | Material | Notes |
|---|---|---|---|
| 5/4 x 6 | 1" x 5-1/2" | Treated, cedar, composite | Standard residential deck board |
| 2 x 4 | 1-1/2" x 3-1/2" | Treated pine, cedar | Narrow deck boards, railings |
| 2 x 6 | 1-1/2" x 5-1/2" | Treated, cedar, redwood | Most common deck board size |
| 2 x 8 | 1-1/2" x 7-1/4" | Treated, cedar | Wide deck boards, benches |
| 2 x 10 | 1-1/2" x 9-1/4" | Treated pine | Deck joists, stair stringers |
| 2 x 12 | 1-1/2" x 11-1/4" | Treated pine | Deck beams, long-span joists |
| 4 x 4 | 3-1/2" x 3-1/2" | Treated, cedar | Deck posts (up to 4' high) |
| 6 x 6 | 5-1/2" x 5-1/2" | Treated, cedar | Deck posts (over 4' high) |
Timber Frame Dimensions
| Size | Typical Use | Weight (Doug Fir, per LF) |
|---|---|---|
| 4 x 6 | Purlins, secondary rafters | 4.7 lbs |
| 6 x 6 | Posts, small beams, braces | 8.0 lbs |
| 6 x 8 | Principal rafters, floor beams | 10.7 lbs |
| 6 x 10 | Ridge beams, floor beams | 13.3 lbs |
| 8 x 8 | Main posts, tie beams | 14.2 lbs |
| 8 x 10 | Summer beams, heavy rafters | 17.8 lbs |
| 8 x 12 | Major beams, girders | 21.3 lbs |
| 10 x 10 | Main posts, bent girts | 22.2 lbs |
| 10 x 12 | Summer beams, main girders | 26.7 lbs |
| 12 x 12 | Sill beams, main posts | 32.0 lbs |
| 12 x 16 | Major girders, bridge beams | 42.7 lbs |
Board Foot Calculator
Understanding board feet (BF) -- the standard unit for purchasing hardwood and reclaimed lumber
The Formula
Board Feet = (T x W x L) / 144
Where T = Thickness (in), W = Width (in), L = Length (in)
A board foot is a volume measurement equal to a piece of wood 12 inches long, 12 inches wide, and 1 inch thick (144 cubic inches). It is the standard unit for buying and selling hardwood lumber in North America.
Alternative formula: If your length is in feet instead of inches:
Board Feet = (T x W x L) / 12
Where T = Thickness (in), W = Width (in), L = Length (ft)
Quick tip: For hardwood, use the nominal (rough) thickness when calculating board feet. A 4/4 board is counted as 1" thick even if surfaced down to 13/16".
Example Calculations
A 4/4 board, 6" wide, 8' long
(1 x 6 x 96) / 144 = 4.0 BF
or (1 x 6 x 8) / 12 = 4.0 BF
An 8/4 board, 10" wide, 12' long
(2 x 10 x 144) / 144 = 20.0 BF
or (2 x 10 x 12) / 12 = 20.0 BF
A 5/4 board, 8" wide, 6' long
(1.25 x 8 x 72) / 144 = 5.0 BF
or (1.25 x 8 x 6) / 12 = 5.0 BF
A 6/4 board, 5" wide, 10' long
(1.5 x 5 x 120) / 144 = 6.25 BF
or (1.5 x 5 x 10) / 12 = 6.25 BF
A 12/4 board, 12" wide, 8' long
(3 x 12 x 96) / 144 = 24.0 BF
or (3 x 12 x 8) / 12 = 24.0 BF
Weight per Board Foot by Species
Approximate weight at 8% moisture content -- useful for shipping estimates and structural calculations
| Species | Density (lbs/ft³) | Weight per BF (lbs) | Weight per 100 BF (lbs) | Category |
|---|---|---|---|---|
| Eastern White Pine | 25 | 2.08 | 208 | Light |
| Hemlock | 28 | 2.33 | 233 | Light |
| Cypress | 32 | 2.67 | 267 | Medium-Light |
| Douglas Fir | 32 | 2.67 | 267 | Medium-Light |
| Poplar | 29 | 2.42 | 242 | Light |
| American Chestnut | 30 | 2.50 | 250 | Medium-Light |
| Eastern Red Cedar | 33 | 2.75 | 275 | Medium |
| Cherry | 35 | 2.92 | 292 | Medium |
| Black Walnut | 38 | 3.17 | 317 | Medium |
| Heart Pine | 39 | 3.25 | 325 | Medium-Heavy |
| White Ash | 42 | 3.50 | 350 | Heavy |
| Yellow Birch | 43 | 3.58 | 358 | Heavy |
| Red Oak | 44 | 3.67 | 367 | Heavy |
| Hard Maple | 44 | 3.67 | 367 | Heavy |
| American Beech | 45 | 3.75 | 375 | Heavy |
| White Oak | 47 | 3.92 | 392 | Heavy |
Coverage Calculations by Application
How many board feet, linear feet, or square feet you need for different applications
Flooring Coverage
| Board Width | BF per 100 SF | Add Waste |
|---|---|---|
| 2-1/4" strip | 100 BF | +15-20% |
| 3-1/4" plank | 100 BF | +15-20% |
| 5" plank | 100 BF | +15-20% |
| 7" wide plank | 100 BF | +15-20% |
| T&G (any width) | 115-120 BF | +15-20% |
T&G: tongue-and-groove profiles reduce coverage by 10-15% due to overlap.
Siding Coverage
| Profile | BF per 100 SF | Overlap Factor |
|---|---|---|
| Clapboard (6") | 130-140 BF | 1" overlap |
| Board & Batten | 120-130 BF | 1/2" overlap |
| Shiplap (6") | 115-120 BF | 3/8" overlap |
| Channel Siding | 115-120 BF | 1/2" overlap |
| Vertical T&G | 110-115 BF | Standard T&G |
Add 10-15% for waste. Add 5% for gable ends and trim cuts.
Decking Coverage
| Board Size | LF per 100 SF | Spacing |
|---|---|---|
| 5/4 x 6 (actual 5-1/2") | 220 LF | 1/8" gap |
| 2 x 4 (actual 3-1/2") | 340 LF | 1/8" gap |
| 2 x 6 (actual 5-1/2") | 220 LF | 1/8" gap |
| 2 x 8 (actual 7-1/4") | 167 LF | 1/8" gap |
| 1 x 4 (actual 3-1/2") | 340 LF | 1/8" gap |
Add 10-15% for waste. Diagonal patterns add 15-20%.
Stack & Bundle Sizes for Ordering
| Bundle Type | Typical BF | Approx. Weight |
|---|---|---|
| Small bundle (4/4 random) | 50-100 BF | 150-400 lbs |
| Standard unit (4/4 hardwood) | 500-600 BF | 1,500-2,200 lbs |
| Standard unit (softwood) | 300-500 BF | 700-1,200 lbs |
| Beam lot (6x6 to 8x8) | 200-400 BF | 600-1,500 lbs |
| Timber lot (10x10+) | 300-800 BF | 1,000-3,000 lbs |
| Pallet of shorts (under 4') | 100-200 BF | 300-700 lbs |
| Flooring bundle (T&G) | 200-300 SF | 600-1,100 lbs |
Reclaimed Lumber Sizing Tolerances
Reclaimed lumber does not conform to modern ASTM dimensional tolerances. Due to its age, previous use, and the milling standards of its era, reclaimed stock exhibits wider dimensional variation than new lumber. Below are typical tolerances for reclaimed lumber at Boston Lumber.
| Category | Tolerance |
|---|---|
| Rough-sawn thickness | +/- 1/8" to 1/4" |
| Rough-sawn width | +/- 1/8" to 3/8" |
| Surfaced thickness (after planing) | +/- 1/32" |
| Surfaced width (after ripping) | +/- 1/16" |
| Length (rough) | +/- 1" (cut long, never short) |
| Length (cut to spec) | +/- 1/16" |
| Hand-hewn beams (cross-section) | +/- 1/2" to 1" per face |
| Tongue & groove fit | Tight fit, 1/64" gap max |
Board Feet Quick Reference
Board feet per piece for common 4/4 (1" thick) lumber sizes
| Width | 4' Long | 6' Long | 8' Long | 10' Long | 12' Long | 14' Long | 16' Long | 20' Long |
|---|---|---|---|---|---|---|---|---|
| 2" | 0.67 | 1.00 | 1.33 | 1.67 | 2.00 | 2.33 | 2.67 | 3.33 |
| 3" | 1.00 | 1.50 | 2.00 | 2.50 | 3.00 | 3.50 | 4.00 | 5.00 |
| 4" | 1.33 | 2.00 | 2.67 | 3.33 | 4.00 | 4.67 | 5.33 | 6.67 |
| 5" | 1.67 | 2.50 | 3.33 | 4.17 | 5.00 | 5.83 | 6.67 | 8.33 |
| 6" | 2.00 | 3.00 | 4.00 | 5.00 | 6.00 | 7.00 | 8.00 | 10.00 |
| 8" | 2.67 | 4.00 | 5.33 | 6.67 | 8.00 | 9.33 | 10.67 | 13.33 |
| 10" | 3.33 | 5.00 | 6.67 | 8.33 | 10.00 | 11.67 | 13.33 | 16.67 |
| 12" | 4.00 | 6.00 | 8.00 | 10.00 | 12.00 | 14.00 | 16.00 | 20.00 |
| 14" | 4.67 | 7.00 | 9.33 | 11.67 | 14.00 | 16.33 | 18.67 | 23.33 |
| 16" | 5.33 | 8.00 | 10.67 | 13.33 | 16.00 | 18.67 | 21.33 | 26.67 |
Multiplier for thicker stock: For 5/4 lumber, multiply values by 1.25. For 6/4, multiply by 1.5. For 8/4, multiply by 2. For 12/4, multiply by 3. For 16/4, multiply by 4.
Standard Lumber Lengths
Available lengths for dimensional lumber, hardwood, and reclaimed stock
Softwood Dimensional
| Feet | Inches | Meters |
|---|---|---|
| 6' | 72" | 1.83 |
| 8' | 96" | 2.44 |
| 10' | 120" | 3.05 |
| 12' | 144" | 3.66 |
| 14' | 168" | 4.27 |
| 16' | 192" | 4.88 |
| 18' | 216" | 5.49 |
| 20' | 240" | 6.10 |
| 22' | 264" | 6.71 |
| 24' | 288" | 7.32 |
Hardwood Random Lengths
Hardwood is typically sold in random widths and lengths:
| Grade | Min | Range |
|---|---|---|
| FAS | 6' | 8'-16' |
| FAS One Face | 6' | 8'-16' |
| Select | 6' | 6'-14' |
| No. 1 Common | 4' | 4'-12' |
| No. 2 Common | 3' | 3'-10' |
| No. 3 Common | 2' | 2'-8' |
Reclaimed Lumber
Lengths vary based on source structure:
| Source | Range |
|---|---|
| Barns & Farmsteads | 4'-20'+ |
| Industrial Buildings | 6'-24'+ |
| Factories & Mills | 8'-30'+ |
| Railroad Ties | 8'-9' |
| Shipping Pallets | 3'-4' |
| Gymnasium Floors | 1'-8' |
| Wine/Whiskey Barrels | 2'-3' |
| Fence/Corral Boards | 6'-16' |
Metric Conversion Reference
Quick conversion tables for international customers
| Inches | Millimeters | Centimeters |
|---|---|---|
| 1/4" | 6.350 | 0.635 |
| 1/2" | 12.700 | 1.270 |
| 3/4" | 19.050 | 1.905 |
| 1" | 25.400 | 2.540 |
| 1-1/2" | 38.100 | 3.810 |
| 2" | 50.800 | 5.080 |
| 3" | 76.200 | 7.620 |
| 3-1/2" | 88.900 | 8.890 |
| 4" | 101.600 | 10.160 |
| 5-1/2" | 139.700 | 13.970 |
| 7-1/4" | 184.150 | 18.415 |
| 9-1/4" | 234.950 | 23.495 |
| 11-1/4" | 285.750 | 28.575 |
| Feet | Meters | Centimeters |
|---|---|---|
| 1' | 0.305 | 30.48 |
| 2' | 0.610 | 60.96 |
| 4' | 1.219 | 121.92 |
| 6' | 1.829 | 182.88 |
| 8' | 2.438 | 243.84 |
| 10' | 3.048 | 304.80 |
| 12' | 3.658 | 365.76 |
| 14' | 4.267 | 426.72 |
| 16' | 4.877 | 487.68 |
| 20' | 6.096 | 609.60 |
| 24' | 7.315 | 731.52 |
Volume: 1 board foot = 2,359.74 cm³ = 0.002360 m³
Weight estimates: Softwood averages 25-35 lbs/ft³ (400-560 kg/m³). Hardwood averages 35-55 lbs/ft³ (560-880 kg/m³).
Size Guide FAQs
Common questions about lumber dimensions, sizing, and ordering
Why are nominal and actual dimensions different?
When lumber is first sawn from a log, it is cut to the nominal dimension (e.g., 2 inches). During drying and planing (surfacing), material is removed from all faces, reducing the final actual dimension. Modern standards (established in the 1960s) define the amount of material removed during surfacing: 1/2 inch from each dimension for lumber 2 inches and thicker, and 1/4 inch for lumber under 2 inches. Reclaimed lumber often predates these standards and may be closer to true nominal size.
Can you custom-mill reclaimed lumber to specific dimensions?
Yes. Our on-site milling facility can surface, rip, resaw, and profile reclaimed lumber to any dimension you need. We can match existing dimensions for renovation projects, create non-standard sizes, or produce traditional profiles that are no longer commercially available. Custom milling fees depend on the complexity of the work and the volume of material. Contact info@boston-lumber.com for a milling quote.
How do I convert between board feet, linear feet, and square feet?
Board feet is a volume measurement (T x W x L / 144 in cubic inches). Linear feet measures length only. Square feet measures area. To convert: for 4/4 (1-inch) lumber, 1 BF = 1 square foot of coverage. For thicker stock, divide BF by the thickness in inches to get square footage. For linear feet, multiply the square footage by 12 and divide by the board width in inches.
What is the difference between rough-sawn and surfaced lumber?
Rough-sawn lumber comes straight from the saw with a textured surface and slight dimensional variation. Surfaced lumber (also called planed, dressed, or S4S -- surfaced four sides) has been run through a planer to create smooth, consistent faces and edges. Surfacing removes approximately 1/16 to 1/8 inch from each face. Rough-sawn is less expensive and preferred when the surface will be hidden or when you want to plane to your own exact dimension.
How should I measure reclaimed lumber before ordering?
Measure actual dimensions (not nominal) at multiple points along each board, as reclaimed lumber can vary. Measure thickness, width, and length. Note any taper (width change along the length). Measure at the narrowest point if you need a guaranteed minimum dimension. For large orders, provide us with your cutting list and we will calculate the total board footage needed, including waste factor.
What waste factor should I use when ordering reclaimed lumber?
We recommend 15-20% waste factor for reclaimed lumber, compared to the standard 10% for new lumber. The additional waste accounts for nail holes, end checks, unusable sections, and the natural variation in reclaimed stock. For tongue-and-groove applications, add another 10-15% for the material lost to the profile overlap. For complex cutting patterns (herringbone, diagonal), add 20-25% waste factor.
Can reclaimed lumber be obtained in widths over 12 inches?
Yes, and this is one of the great advantages of reclaimed lumber. Old-growth trees produced much wider boards than modern plantation-grown timber. We regularly stock reclaimed boards 14 to 24 inches wide in species like white pine, chestnut, and oak. Widths over 18 inches command a premium due to their rarity, but they are available. These wide boards are prized for tabletops, bar tops, and architectural paneling.
How do I estimate shipping weight for my order?
Use our weight-per-board-foot table above. Multiply the weight per BF by your total board footage. For example, 500 BF of white oak at 3.92 lbs/BF = approximately 1,960 lbs. Add 5-10% for banding, stickers, and pallet weight. For rough estimates: softwood orders average about 2.5 lbs/BF and hardwood orders average about 3.5 lbs/BF. Reclaimed wood may be slightly lighter than new stock of the same species due to long-term drying.