About

Lumber pricing operates on the board foot standard - a unit representing 144 in³ of wood, equivalent to a 1″ × 12″ × 12″ volume. Miscalculating board feet leads to material shortages mid-project or budget overruns from excess purchases. The critical distinction between nominal and actual dimensions compounds errors: a "2×4" measures 1.5″ × 3.5″ after milling, representing a 34% volume reduction from the labeled size.

This calculator handles both dimension systems, applies configurable waste factors for cuts and defects, and aggregates multiple lumber items into total board footage with cost estimation. Standard practice in sawmills and lumber yards prices hardwoods per board foot while softwood construction lumber often sells by linear foot or piece - verify your supplier's pricing unit before ordering.

Formulas

The board foot represents a volumetric unit standardized across the North American lumber industry. One board foot equals a piece 1 inch thick, 12 inches wide, and 12 inches long.

BF = T × W × L144

Where T = thickness in inches, W = width in inches, L = length in inches. When length is measured in feet, the formula simplifies:

BF = T × W × L_ft12

Applying a waste factor for saw kerf, defects, and cutting errors:

BF_adjusted = BF × (1 + W_%100)

Total project cost calculation:

Cost = BF_total × P

Where P = price per board foot in your local currency.

Reference Data

Nominal Size	Actual Size (inches)	Actual Size (mm)	BF per Linear Foot	Common Use
1×2	0.75 × 1.5	19 × 38	0.094	Furring strips, trim
1×4	0.75 × 3.5	19 × 89	0.219	Shelving, trim boards
1×6	0.75 × 5.5	19 × 140	0.344	Fence boards, shelving
1×8	0.75 × 7.25	19 × 184	0.453	Siding, wide trim
1×10	0.75 × 9.25	19 × 235	0.578	Wide boards, sheathing
1×12	0.75 × 11.25	19 × 286	0.703	Shelving, wide stock
2×2	1.5 × 1.5	38 × 38	0.188	Balusters, light framing
2×4	1.5 × 3.5	38 × 89	0.438	Wall studs, framing
2×6	1.5 × 5.5	38 × 140	0.688	Floor joists, rafters
2×8	1.5 × 7.25	38 × 184	0.906	Headers, floor joists
2×10	1.5 × 9.25	38 × 235	1.156	Floor joists, beams
2×12	1.5 × 11.25	38 × 286	1.406	Ridge boards, headers
4×4	3.5 × 3.5	89 × 89	1.021	Posts, columns
4×6	3.5 × 5.5	89 × 140	1.604	Beams, posts
6×6	5.5 × 5.5	140 × 140	2.521	Heavy posts, timber frame
6×8	5.5 × 7.5	140 × 190	3.438	Timber frame beams
8×8	7.5 × 7.5	190 × 190	4.688	Heavy timber construction
4/4 (Hardwood)	0.8125 (surfaced)	21	Varies	Furniture, cabinetry
5/4 (Hardwood)	1.0625 (surfaced)	27	Varies	Decking, thick panels
6/4 (Hardwood)	1.3125 (surfaced)	33	Varies	Table tops, heavy furniture
8/4 (Hardwood)	1.8125 (surfaced)	46	Varies	Workbenches, thick stock
10/4 (Hardwood)	2.3125 (surfaced)	59	Varies	Turning blanks, heavy work
12/4 (Hardwood)	2.8125 (surfaced)	71	Varies	Large turnings, beams
16/4 (Hardwood)	3.8125 (surfaced)	97	Varies	Specialty thick stock

Frequently Asked Questions

Nominal dimensions reflect the rough-sawn size before drying and planing. A 2×4 starts as 2″ × 4″ rough lumber but shrinks during kiln drying (losing approximately 6-8% moisture) and loses material during surfacing (planing smooth). The resulting 1.5″ × 3.5″ actual size is standardized by the American Lumber Standard Committee (ALSC). This discrepancy matters critically for board foot calculations - using nominal dimensions overstates volume by 20-35% depending on the lumber size.

Hardwood lumber uses quarter-inch notation where the numerator indicates thickness in quarter-inches. 4/4 ("four-quarter") means 1″ rough thickness, 8/4 means 2″ rough. After surfacing, 4/4 yields approximately 13/16″ (0.8125″) finished thickness. Board foot calculations for hardwoods typically use the rough (pre-surfaced) thickness since that's how sawmills price the material. A 4/4 board 6″ wide and 8′ long contains 4 board feet regardless of whether you later surface it to 3/4″.

Industry standards suggest 10-15% waste for straightforward projects with long, straight cuts. Increase to 20-25% for projects requiring many short pieces or angled cuts. Complex furniture with curved components or intricate joinery may require 30% or more. Reclaimed or lower-grade lumber with defects (knots, checks, wane) can demand 35-50% extra material. The saw kerf itself consumes 1/8″ to 3/16″ per cut, which compounds across multiple pieces.

Match your calculation method to how the lumber is sold. Sawmills and hardwood dealers typically price rough lumber using pre-surfacing dimensions - a 4/4 board is calculated at 1″ thick even if you buy it already surfaced to 13/16″. Big-box stores selling dimensional softwood (2×4, 2×6) often price by the piece or linear foot rather than board foot, making the distinction less relevant. When estimating material needs for a project, use the finished dimensions you actually need, then add waste factor.

One board foot equals 1/12 cubic foot or approximately 0.00236 cubic meters. Multiply your total board feet by 0.00236 to get cubic meters. The inverse: multiply cubic meters by 423.78 to get board feet. International lumber often trades in cubic meters, particularly for container shipments. A standard 20-foot shipping container holds roughly 25-28 cubic meters of lumber, equivalent to approximately 10,600-11,900 board feet depending on stacking efficiency.

Nominal mode uses the labeled lumber dimensions (2×4 = 2″ × 4″), which matches how rough-sawn lumber at sawmills is measured. Actual mode uses real post-surfacing dimensions (2×4 = 1.5″ × 3.5″), reflecting what you physically receive from lumber yards selling dimensional lumber. The difference matters for accurate material estimation: using nominal dimensions for actual lumber overstates your board footage by roughly 34% for a 2×4 and 21% for a 2×12.