Board Feet, Studs & Framing
Last reviewed: May 2026
A lumber calculator converts project dimensions into exact board quantities plus cost estimates. Key concepts: board feet (hardwood), linear feet (dimensional lumber), stud count (framing). Accurate calculation prevents costly over-ordering and frustrating mid-project supply runs.1
| Size | Length | Board Feet | Price |
|---|---|---|---|
| 1x6 | 8 ft | 4 BF | $12–$24 |
| 2x4 | 8 ft | 5.33 BF | $3–$6 |
| 2x6 | 10 ft | 10 BF | $8–$14 |
| 2x10 | 12 ft | 20 BF | $15–$25 |
| Nominal | Actual | Use |
|---|---|---|
| 2x4 | 1.5" x 3.5" | Wall studs |
| 2x6 | 1.5" x 5.5" | Exterior walls |
| 2x10 | 1.5" x 9.25" | Floor joists |
| 2x12 | 1.5" x 11.25" | Long joists, stringers |
Lumber dimensions are among the most confusing measurements in construction. A "2×4" doesn't measure 2 inches by 4 inches — it measures 1.5" × 3.5". The nominal dimensions (2×4, 2×6, 2×8, etc.) represent the rough-sawn size before drying and planing. After processing, each dimension shrinks: boards under 2" nominal lose ¼" (so 1" nominal = ¾" actual), and boards 2" and over lose ½" (so 2" nominal = 1.5" actual). This convention dates to the early 1900s and is standardized by the American Lumber Standard Committee.
Hardwoods and specialty lumber are sold by the board foot — a unit equal to 144 cubic inches (1" × 12" × 12" or equivalent). To calculate board feet: (thickness" × width" × length") ÷ 144. A 2"×6"×8' board = (2 × 6 × 96) ÷ 144 = 8 board feet. Softwood dimensional lumber (framing) is sold by the linear foot or per piece. Plywood and sheet goods are sold by the sheet (4'×8' standard). Understanding these different pricing units prevents costly purchasing mistakes.
Douglas fir: The standard structural framing lumber in western U.S. Strong, straight, moderate cost. SPF (Spruce-Pine-Fir): Common framing lumber in eastern U.S. and Canada. Lighter weight, slightly less strong than Doug fir. Pressure-treated pine: Chemical treatment resists rot and insects. Required for ground contact, decks, and outdoor structures. Cedar: Naturally rot-resistant, beautiful grain. Used for decking, fencing, siding, and closet lining. 2-3× the cost of pine. Oak: Hardwood used for furniture, flooring, and cabinetry. Sold in rough-sawn boards by the board foot. Poplar: Affordable hardwood for painting — takes paint better than most woods.
Framing a wall: Studs every 16" on-center means (wall length in inches ÷ 16) + 1 studs, plus a bottom plate and double top plate. A 12' wall needs 10 studs + 3 plates = 13 pieces of 2×4. Decking: Divide deck area by individual board coverage area. A 5.5"-wide deck board covers 0.458 sq ft per linear foot. A 200 sq ft deck needs approximately 437 linear feet of decking (200 ÷ 0.458), or about 55 boards at 8' lengths — plus 10% waste. Shelving: ¾" plywood or 1× lumber. Standard shelf span without support: 36" for ¾" plywood, 24" for 1× boards. Longer spans need mid-span support to prevent sagging.
Structural lumber is graded by strength: Select Structural (highest, fewest defects), #1 (structural, minor defects), #2 (standard framing grade — most residential construction uses this), #3/Utility (non-structural, blocking, temporary). For appearance lumber (trim, shelving): Clear (no knots), Select (minor imperfections), Common #1-#3 (increasing number of knots). When selecting boards at the store, sight down each board's length to check for twist, bow, and crown. Reject boards with large knots near edges, splits, or significant warp — these get worse as the wood dries further.
The most confusing aspect of buying lumber is that a "2x4" is not 2 inches by 4 inches. After milling and drying, a nominal 2x4 actually measures 1.5" × 3.5". A 2x6 is 1.5" × 5.5", a 2x8 is 1.5" × 7.25", and a 2x12 is 1.5" × 11.25". This matters enormously for project calculations: a wall built with 2x4 studs provides 3.5 inches of cavity depth for insulation, not 4 inches. Dimensional lumber follows consistent shrinkage patterns: boards under 2" nominal lose 1/2" (so 1" nominal = 3/4" actual), while boards 2" and over lose 1/2" in thickness and 1/2" to 3/4" in width. The exception is rough-sawn lumber from specialty mills, which is sold at full nominal dimensions — and is considerably more expensive because it uses more raw material per board.
Hardwood and specialty lumber is sold by the board foot (BF), not by linear foot. One board foot equals 144 cubic inches — a piece 12" long × 12" wide × 1" thick. The formula is: BF = (thickness × width × length) ÷ 144, with all measurements in inches. A board that's 1" thick × 6" wide × 8' long (96") = (1 × 6 × 96) ÷ 144 = 4 board feet. Crucially, hardwood pricing uses nominal thickness — a 4/4 (four-quarter, or 1-inch nominal) board that actually measures 13/16" after surfacing is still calculated as 1" thick for board footage. Common thickness designations: 4/4 = 1", 5/4 = 1.25", 6/4 = 1.5", 8/4 = 2". Cherry at $8/BF for a 5/4 × 8" × 10' board: (1.25 × 8 × 120) ÷ 144 = 8.33 BF × $8 = $66.67. Adding 15-20% waste factor for cuts, defects, and grain matching is standard practice in woodworking project planning.
Lumber intended for ground contact, outdoor structures, or humid environments requires pressure treatment — a process that forces preservative chemicals deep into the wood fiber under high pressure. Treatment levels are rated by preservative retention: Above Ground (AG, 0.15 pcf) for decking and railings, Ground Contact (GC, 0.40 pcf) for posts and framing touching soil, and Heavy Duty Ground Contact (HDGC, 0.60 pcf) for structural members embedded in concrete or freshwater. Using above-ground-rated lumber in ground contact can lead to rot failure within 3-5 years, while properly treated wood lasts 20-40 years in soil. Alternatives include naturally rot-resistant species: cedar (heartwood only, 10-15 years ground contact), redwood (old-growth heartwood, 15-25 years), and tropical hardwoods like ipe (25-50 years, but $8-15/linear foot versus $1-3 for pressure-treated pine). For structural calculations, note that pressure-treated southern yellow pine has slightly different span ratings than untreated — the treatment process can reduce bending strength by 5-10% in some grades.
Framing a standard interior wall requires one bottom plate, one or two top plates, and studs every 16 inches on center. A 12-foot wall needs: 2 or 3 plates at 12' each, plus 10 studs (144" ÷ 16" = 9 spaces, 10 studs including ends), plus 1-2 extra for corners, door/window headers, and cripple studs. For a 12' × 8' wall: roughly 14-16 pieces of 2x4 at 8' length. Decking calculations start with the deck area in square feet, then divide by the face width of your boards (5.5" actual for a nominal 2x6, or 0.458 feet): a 200 sq ft deck needs 200 ÷ 0.458 = 437 linear feet of decking — plus 10-15% for waste cuts and board-end trimming. Joists at 16" on center under that deck require the deck width divided by 1.33 feet: a 10'-wide deck needs about 8 joists spanning the deck's depth, plus rim joists. Always draw your project before buying to count exact pieces and lengths, reducing waste trips and ensuring you buy the right dimensions.
The most confusing aspect of buying lumber is that a "2x4" is not 2 inches by 4 inches. After milling and drying, a nominal 2x4 actually measures 1.5" × 3.5". A 2x6 is 1.5" × 5.5", a 2x8 is 1.5" × 7.25", and a 2x12 is 1.5" × 11.25". This matters enormously for project calculations: a wall built with 2x4 studs provides 3.5 inches of cavity depth for insulation, not 4 inches. Dimensional lumber follows consistent shrinkage patterns: boards under 2" nominal lose 1/2" (so 1" nominal = 3/4" actual), while boards 2" and over lose 1/2" in thickness and 1/2" to 3/4" in width. The exception is rough-sawn lumber from specialty mills, which is sold at full nominal dimensions — and is considerably more expensive because it uses more raw material per board.
Hardwood and specialty lumber is sold by the board foot (BF), not by linear foot. One board foot equals 144 cubic inches — a piece 12" long × 12" wide × 1" thick. The formula is: BF = (thickness × width × length) ÷ 144, with all measurements in inches. A board that's 1" thick × 6" wide × 8' long (96") = (1 × 6 × 96) ÷ 144 = 4 board feet. Crucially, hardwood pricing uses nominal thickness — a 4/4 (four-quarter, or 1-inch nominal) board that actually measures 13/16" after surfacing is still calculated as 1" thick for board footage. Common thickness designations: 4/4 = 1", 5/4 = 1.25", 6/4 = 1.5", 8/4 = 2". Cherry at $8/BF for a 5/4 × 8" × 10' board: (1.25 × 8 × 120) ÷ 144 = 8.33 BF × $8 = $66.67. Adding 15-20% waste factor for cuts, defects, and grain matching is standard practice in woodworking project planning.
Lumber intended for ground contact, outdoor structures, or humid environments requires pressure treatment — a process that forces preservative chemicals deep into the wood fiber under high pressure. Treatment levels are rated by preservative retention: Above Ground (AG, 0.15 pcf) for decking and railings, Ground Contact (GC, 0.40 pcf) for posts and framing touching soil, and Heavy Duty Ground Contact (HDGC, 0.60 pcf) for structural members embedded in concrete or freshwater. Using above-ground-rated lumber in ground contact can lead to rot failure within 3-5 years, while properly treated wood lasts 20-40 years in soil. Alternatives include naturally rot-resistant species: cedar (heartwood only, 10-15 years ground contact), redwood (old-growth heartwood, 15-25 years), and tropical hardwoods like ipe (25-50 years, but $8-15/linear foot versus $1-3 for pressure-treated pine). For structural calculations, note that pressure-treated southern yellow pine has slightly different span ratings than untreated — the treatment process can reduce bending strength by 5-10% in some grades.
Framing a standard interior wall requires one bottom plate, one or two top plates, and studs every 16 inches on center. A 12-foot wall needs: 2 or 3 plates at 12' each, plus 10 studs (144" ÷ 16" = 9 spaces, 10 studs including ends), plus 1-2 extra for corners, door/window headers, and cripple studs. For a 12' × 8' wall: roughly 14-16 pieces of 2x4 at 8' length. Decking calculations start with the deck area in square feet, then divide by the face width of your boards (5.5" actual for a nominal 2x6, or 0.458 feet): a 200 sq ft deck needs 200 ÷ 0.458 = 437 linear feet of decking — plus 10-15% for waste cuts and board-end trimming. Joists at 16" on center under that deck require the deck width divided by 1.33 feet: a 10'-wide deck needs about 8 joists spanning the deck's depth, plus rim joists. Always draw your project before buying to count exact pieces and lengths, reducing waste trips and ensuring you buy the right dimensions.
The most confusing aspect of buying lumber is that a "2x4" is not 2 inches by 4 inches. After milling and drying, a nominal 2x4 actually measures 1.5" × 3.5". A 2x6 is 1.5" × 5.5", a 2x8 is 1.5" × 7.25", and a 2x12 is 1.5" × 11.25". This matters enormously for project calculations: a wall built with 2x4 studs provides 3.5 inches of cavity depth for insulation, not 4 inches. Dimensional lumber follows consistent shrinkage patterns: boards under 2" nominal lose 1/2" (so 1" nominal = 3/4" actual), while boards 2" and over lose 1/2" in thickness and 1/2" to 3/4" in width. The exception is rough-sawn lumber from specialty mills, which is sold at full nominal dimensions — and is considerably more expensive because it uses more raw material per board.
Hardwood and specialty lumber is sold by the board foot (BF), not by linear foot. One board foot equals 144 cubic inches — a piece 12" long × 12" wide × 1" thick. The formula is: BF = (thickness × width × length) ÷ 144, with all measurements in inches. A board that's 1" thick × 6" wide × 8' long (96") = (1 × 6 × 96) ÷ 144 = 4 board feet. Crucially, hardwood pricing uses nominal thickness — a 4/4 (four-quarter, or 1-inch nominal) board that actually measures 13/16" after surfacing is still calculated as 1" thick for board footage. Common thickness designations: 4/4 = 1", 5/4 = 1.25", 6/4 = 1.5", 8/4 = 2". Cherry at $8/BF for a 5/4 × 8" × 10' board: (1.25 × 8 × 120) ÷ 144 = 8.33 BF × $8 = $66.67. Adding 15-20% waste factor for cuts, defects, and grain matching is standard practice in woodworking project planning.
Lumber intended for ground contact, outdoor structures, or humid environments requires pressure treatment — a process that forces preservative chemicals deep into the wood fiber under high pressure. Treatment levels are rated by preservative retention: Above Ground (AG, 0.15 pcf) for decking and railings, Ground Contact (GC, 0.40 pcf) for posts and framing touching soil, and Heavy Duty Ground Contact (HDGC, 0.60 pcf) for structural members embedded in concrete or freshwater. Using above-ground-rated lumber in ground contact can lead to rot failure within 3-5 years, while properly treated wood lasts 20-40 years in soil. Alternatives include naturally rot-resistant species: cedar (heartwood only, 10-15 years ground contact), redwood (old-growth heartwood, 15-25 years), and tropical hardwoods like ipe (25-50 years, but $8-15/linear foot versus $1-3 for pressure-treated pine). For structural calculations, note that pressure-treated southern yellow pine has slightly different span ratings than untreated — the treatment process can reduce bending strength by 5-10% in some grades.
Framing a standard interior wall requires one bottom plate, one or two top plates, and studs every 16 inches on center. A 12-foot wall needs: 2 or 3 plates at 12' each, plus 10 studs (144" ÷ 16" = 9 spaces, 10 studs including ends), plus 1-2 extra for corners, door/window headers, and cripple studs. For a 12' × 8' wall: roughly 14-16 pieces of 2x4 at 8' length. Decking calculations start with the deck area in square feet, then divide by the face width of your boards (5.5" actual for a nominal 2x6, or 0.458 feet): a 200 sq ft deck needs 200 ÷ 0.458 = 437 linear feet of decking — plus 10-15% for waste cuts and board-end trimming. Joists at 16" on center under that deck require the deck width divided by 1.33 feet: a 10'-wide deck needs about 8 joists spanning the deck's depth, plus rim joists. Always draw your project before buying to count exact pieces and lengths, reducing waste trips and ensuring you buy the right dimensions.
The most confusing aspect of buying lumber is that a "2x4" is not 2 inches by 4 inches. After milling and drying, a nominal 2x4 actually measures 1.5" × 3.5". A 2x6 is 1.5" × 5.5", a 2x8 is 1.5" × 7.25", and a 2x12 is 1.5" × 11.25". This matters enormously for project calculations: a wall built with 2x4 studs provides 3.5 inches of cavity depth for insulation, not 4 inches. Dimensional lumber follows consistent shrinkage patterns: boards under 2" nominal lose 1/2" (so 1" nominal = 3/4" actual), while boards 2" and over lose 1/2" in thickness and 1/2" to 3/4" in width. The exception is rough-sawn lumber from specialty mills, which is sold at full nominal dimensions — and is considerably more expensive because it uses more raw material per board.
Hardwood and specialty lumber is sold by the board foot (BF), not by linear foot. One board foot equals 144 cubic inches — a piece 12" long × 12" wide × 1" thick. The formula is: BF = (thickness × width × length) ÷ 144, with all measurements in inches. A board that's 1" thick × 6" wide × 8' long (96") = (1 × 6 × 96) ÷ 144 = 4 board feet. Crucially, hardwood pricing uses nominal thickness — a 4/4 (four-quarter, or 1-inch nominal) board that actually measures 13/16" after surfacing is still calculated as 1" thick for board footage. Common thickness designations: 4/4 = 1", 5/4 = 1.25", 6/4 = 1.5", 8/4 = 2". Cherry at $8/BF for a 5/4 × 8" × 10' board: (1.25 × 8 × 120) ÷ 144 = 8.33 BF × $8 = $66.67. Adding 15-20% waste factor for cuts, defects, and grain matching is standard practice in woodworking project planning.
Lumber intended for ground contact, outdoor structures, or humid environments requires pressure treatment — a process that forces preservative chemicals deep into the wood fiber under high pressure. Treatment levels are rated by preservative retention: Above Ground (AG, 0.15 pcf) for decking and railings, Ground Contact (GC, 0.40 pcf) for posts and framing touching soil, and Heavy Duty Ground Contact (HDGC, 0.60 pcf) for structural members embedded in concrete or freshwater. Using above-ground-rated lumber in ground contact can lead to rot failure within 3-5 years, while properly treated wood lasts 20-40 years in soil. Alternatives include naturally rot-resistant species: cedar (heartwood only, 10-15 years ground contact), redwood (old-growth heartwood, 15-25 years), and tropical hardwoods like ipe (25-50 years, but $8-15/linear foot versus $1-3 for pressure-treated pine). For structural calculations, note that pressure-treated southern yellow pine has slightly different span ratings than untreated — the treatment process can reduce bending strength by 5-10% in some grades.
Framing a standard interior wall requires one bottom plate, one or two top plates, and studs every 16 inches on center. A 12-foot wall needs: 2 or 3 plates at 12' each, plus 10 studs (144" ÷ 16" = 9 spaces, 10 studs including ends), plus 1-2 extra for corners, door/window headers, and cripple studs. For a 12' × 8' wall: roughly 14-16 pieces of 2x4 at 8' length. Decking calculations start with the deck area in square feet, then divide by the face width of your boards (5.5" actual for a nominal 2x6, or 0.458 feet): a 200 sq ft deck needs 200 ÷ 0.458 = 437 linear feet of decking — plus 10-15% for waste cuts and board-end trimming. Joists at 16" on center under that deck require the deck width divided by 1.33 feet: a 10'-wide deck needs about 8 joists spanning the deck's depth, plus rim joists. Always draw your project before buying to count exact pieces and lengths, reducing waste trips and ensuring you buy the right dimensions.
The most confusing aspect of buying lumber is that a "2x4" is not 2 inches by 4 inches. After milling and drying, a nominal 2x4 actually measures 1.5" × 3.5". A 2x6 is 1.5" × 5.5", a 2x8 is 1.5" × 7.25", and a 2x12 is 1.5" × 11.25". This matters enormously for project calculations: a wall built with 2x4 studs provides 3.5 inches of cavity depth for insulation, not 4 inches. Dimensional lumber follows consistent shrinkage patterns: boards under 2" nominal lose 1/2" (so 1" nominal = 3/4" actual), while boards 2" and over lose 1/2" in thickness and 1/2" to 3/4" in width. The exception is rough-sawn lumber from specialty mills, which is sold at full nominal dimensions — and is considerably more expensive because it uses more raw material per board.
Hardwood and specialty lumber is sold by the board foot (BF), not by linear foot. One board foot equals 144 cubic inches — a piece 12" long × 12" wide × 1" thick. The formula is: BF = (thickness × width × length) ÷ 144, with all measurements in inches. A board that's 1" thick × 6" wide × 8' long (96") = (1 × 6 × 96) ÷ 144 = 4 board feet. Crucially, hardwood pricing uses nominal thickness — a 4/4 (four-quarter, or 1-inch nominal) board that actually measures 13/16" after surfacing is still calculated as 1" thick for board footage. Common thickness designations: 4/4 = 1", 5/4 = 1.25", 6/4 = 1.5", 8/4 = 2". Cherry at $8/BF for a 5/4 × 8" × 10' board: (1.25 × 8 × 120) ÷ 144 = 8.33 BF × $8 = $66.67. Adding 15-20% waste factor for cuts, defects, and grain matching is standard practice in woodworking project planning.
Lumber intended for ground contact, outdoor structures, or humid environments requires pressure treatment — a process that forces preservative chemicals deep into the wood fiber under high pressure. Treatment levels are rated by preservative retention: Above Ground (AG, 0.15 pcf) for decking and railings, Ground Contact (GC, 0.40 pcf) for posts and framing touching soil, and Heavy Duty Ground Contact (HDGC, 0.60 pcf) for structural members embedded in concrete or freshwater. Using above-ground-rated lumber in ground contact can lead to rot failure within 3-5 years, while properly treated wood lasts 20-40 years in soil. Alternatives include naturally rot-resistant species: cedar (heartwood only, 10-15 years ground contact), redwood (old-growth heartwood, 15-25 years), and tropical hardwoods like ipe (25-50 years, but $8-15/linear foot versus $1-3 for pressure-treated pine). For structural calculations, note that pressure-treated southern yellow pine has slightly different span ratings than untreated — the treatment process can reduce bending strength by 5-10% in some grades.
Framing a standard interior wall requires one bottom plate, one or two top plates, and studs every 16 inches on center. A 12-foot wall needs: 2 or 3 plates at 12' each, plus 10 studs (144" ÷ 16" = 9 spaces, 10 studs including ends), plus 1-2 extra for corners, door/window headers, and cripple studs. For a 12' × 8' wall: roughly 14-16 pieces of 2x4 at 8' length. Decking calculations start with the deck area in square feet, then divide by the face width of your boards (5.5" actual for a nominal 2x6, or 0.458 feet): a 200 sq ft deck needs 200 ÷ 0.458 = 437 linear feet of decking — plus 10-15% for waste cuts and board-end trimming. Joists at 16" on center under that deck require the deck width divided by 1.33 feet: a 10'-wide deck needs about 8 joists spanning the deck's depth, plus rim joists. Always draw your project before buying to count exact pieces and lengths, reducing waste trips and ensuring you buy the right dimensions.
→ Always add 10–15% waste. A mid-project lumber run costs more in time than extra material.
→ Use actual dimensions. Nominal sizes are labels, not measurements.
→ Check boards for straightness. Sight down the length at the store.
→ Use pressure-treated for ground contact. Untreated wood rots in 2–5 years.
See also: Concrete · Drywall · Paint · Roofing