How Many Board Feet of Lumber Do I Need? (2026 Guide)
How many board feet of lumber do I need? Board feet = (thickness in × width in × length ft) ÷ 12 — a single 2×4×8 is 5.33 bd ft. Formula, chart and example.
What a board foot is
A board foot is a lumber volume unit: 1 ft long × 1 ft wide × 1 in thick = 144 cubic inches. Lumber is labeled by its nominal (named) size, and board foot math normally uses those nominal numbers — the finished piece measures a little less, explained below.
The formula
bd ft = (thickness in × width in × length ft) ÷ 12: multiply the nominal thickness and width in inches by the length in feet, then divide by 12. A 2×4×8: 2 × 4 × 8 = 64, ÷ 12 = 5.33 bd ft.
1. Use nominal thickness and width
Pricing usually counts the nominal “2” and “4” of a 2×4, not the 1½ × 3½ in it actually measures. Most yards bill this way for dimension lumber, but methods vary — your supplier's measuring basis governs the invoice, so confirm it when ordering.
2. Keep the length in feet
Lengths are sold in feet, so the formula divides by 12. Measuring in inches? Divide by 144 instead — a 96-in 2×4 is (2 × 4 × 96) ÷ 144 = 5.33 bd ft.
3. Multiply, then divide
Check: a 2×6×8 is 2 × 6 × 8 = 96, ÷ 12 = 8 bd ft — it matches the chart below.
Board feet per board: quick reference
Nominal size by common length; values are per single board:
| Board (nominal) | Common lengths |
|---|---|
| 2×4 | 8 ft: 5.33 · 10 ft: 6.67 · 12 ft: 8 · 16 ft: 10.67 |
| 2×6 | 8 ft: 8 · 10 ft: 10 · 12 ft: 12 · 16 ft: 16 |
| 2×8 | 8 ft: 10.67 · 12 ft: 16 · 16 ft: 21.33 |
| 1×6 | 8 ft: 4 · 10 ft: 5 · 12 ft: 6 |
Each entry is the formula in action: a 2×6×10 is 2 × 6 × 10 = 120, ÷ 12 = 10 bd ft. Missing pairs follow the same math — the board foot calculator handles any size and length.
Worked example: 10 boards of 2×4×8
Ten 2×4×8s at 5.33 bd ft each: 10 × 5.33 ≈ 53 bd ft. With a 10% waste allowance for framing cuts and split ends, order about 58 bd ft.
Budgeting is just as quick: at $2.50 per board foot, a 500 bd ft order runs $1,250. Prices vary by species, grade and region — use the rate your supplier quotes.
Ordering tips
- Nominal vs. actual — a “2×4” measures about 1½ × 3½ in after surfacing, yet totals are usually figured on the nominal 2×4. Confirm which basis a quote uses.
- Add 5–10% for waste — cut-offs, split ends and the odd bad board eat real volume, so round the order up and return leftovers.
- Board feet vs. linear feet — board feet charge volume (thickness × width × length); linear feet charge length alone. Convert every quote to the same unit before comparing.
Ordering decking or framing next? The same count-then-order logic applies to deck boards for a deck and rafters for a roof.
FAQ
What's the difference between board feet and linear feet?
Board feet measure volume: nominal thickness and width in inches times length in feet, divided by 12. Linear feet measure length only — a 2×4×8 is 5.33 bd ft and 8 linear ft, the same board in two units. Trim and molding are priced per linear foot; bulk lumber per board foot. Compare quotes on the same unit.
Does a board foot estimate based on nominal size include waste?
No. The math totals the full volume of every board you order and subtracts nothing for cut-offs, knots or split ends, so add 5–10% for waste on top. Nominal-size billing is the usual practice for dimension lumber, but your supplier's measuring method is what shows up on the invoice — confirm it with the quote.
Why isn't a 2×4 actually 2 by 4 inches?
The “2×4” is the nominal size — what the board measured rough-sawn before drying and planing dressed it down to about 1½ × 3½ in. The labels stuck, so lumber is still measured for board feet on the nominal 2×4 figure.
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