How do I calculate board feet?
A board foot is 144 cubic inches of wood: a piece 1 in thick, 12 in wide and 1 ft long. Multiply the nominal thickness by the nominal width in inches, multiply by the length in feet, and divide by 12.
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
Ten 2×6 boards, 12 ft long: 2 × 6 × 12 ÷ 12 = 12 board feet each, or 120 board feet in total. At $0.80 per board foot that's $9.60 a board and $96 for all ten.
Dimensional lumber is counted at its nominal size. A 2×6 actually measures 1.5 × 5.5 in, but it's sold and counted as 2 × 6.
Board feet per piece
| Size | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|
| 1×6 | 4.00 | 5.00 | 6.00 | 8.00 |
| 2×4 | 5.33 | 6.67 | 8.00 | 10.67 |
| 2×6 | 8.00 | 10.00 | 12.00 | 16.00 |
| 2×8 | 10.67 | 13.33 | 16.00 | 21.33 |
| 2×10 | 13.33 | 16.67 | 20.00 | 26.67 |
| 2×12 | 16.00 | 20.00 | 24.00 | 32.00 |
| 4×4 | 10.67 | 13.33 | 16.00 | 21.33 |
| 6×6 | 24.00 | 30.00 | 36.00 | 48.00 |
Price per board foot or per piece
Lumber yards often quote hardwood and some framing lumber by the board foot, and home centers price by the piece. Switch "Price by" to compare. Enter a piece price and the calculator shows what it works out to per board foot, which is the fair way to compare a 2×6 × 12 with a 2×8 × 16.
The default prices are rough 2026 figures and change often. Replace them with your yard's prices.
Wall framing: studs and plates
For a wall, studs go at 16 or 24 in on center. Divide the wall length by the spacing, add one for the end, then add studs for corners, wall intersections and openings. A wall usually has three plates: one bottom plate and a double top plate.
Studs = wall length (in) ÷ spacing + 1 + 2 per corner + 2 per opening + extra
A 20 ft wall at 16 in on center: 240 ÷ 16 = 15, plus 1 = 16 studs. With 10% extra for crooked boards, buy 18. The plates are 3 × 20 = 60 ft, so four 16 ft boards. Stagger the joints in the double top plate at least 24 in apart, as the IRC requires.
Precut studs are sized so a wall with a single bottom plate and double top plate comes out at the ceiling height. 92-5/8 in studs make an 8 ft wall, 104-5/8 in make 9 ft and 116-5/8 in make 10 ft. Headers, cripples, blocking and sheathing aren't counted, so add them separately.
Deck lumber calculator
For a deck, use the deck calculator. It counts decking, joists, ledger and rim, beams and posts from the deck's size. Use this page to price any extra pieces, such as blocking or fascia, by length and count. Joist and beam sizes come from your local span tables, not from a calculator.
Pricing a framing job
Carpenters usually price framing as lumber at cost plus markup, with labor by the hour or by the square foot of wall or floor. Switch to contractor mode in wall framing to add your labor rate, then send it as an estimate.
Questions
How many board feet are in a 2x4x8?
5.33 board feet: 2 x 4 x 8 divided by 12.
How many studs do I need for a wall?
Wall length in inches divided by the stud spacing, plus one, plus about 2 for each corner and opening. A 20 ft wall at 16 inches on center needs 16 studs before extra.
Why is a 2x4 not 2 inches by 4 inches?
The nominal size is the rough-sawn size. After drying and planing, a 2x4 measures 1.5 x 3.5 inches. Board feet still use the nominal size.
How many plates does a wall need?
Usually three: one bottom plate and a double top plate, so plate length is three times the wall length.