How this calculator works
A board foot is a volume measurement − one square foot of lumber that is one inch thick, or 144 cubic inches. It exists so that lumber of any size can be priced against the same yardstick: a 1×6, a 2×10, and a 4×4 are all comparable in board feet. The calculator takes your board dimensions, multiplies thickness × width × length in inches, divides by 144, then multiplies by quantity and adds waste. It shows both the actual board feet (what you measure in hand) and the nominal board feet (what the yard sells it as).
Board feet = (T in × W in × L in) ÷ 144
Total BF = BF per piece × Pieces × (1 + Waste%)
Most trade pricing uses nominal board feet − the size the lumber was before drying and dressing. That is why a 2×4×8 is sold as 5.33 board feet even though the actual volume is 3.5 board feet. If you are buying finished stock by the piece and pricing it yourself, use actual board feet. The dropdown lets you choose which one applies to your quote.
Nominal vs actual lumber dimensions
Every dimensional lumber size you buy in the US is nominal − a name, not a measurement. A 2×4 is not 2 inches by 4 inches. It is 1.5 inches by 3.5 inches, because the boards are planed down after milling to make them consistent. This is the single most common source of estimating error in lumber projects.
| Nominal size | Actual size | Board feet (nominal) | Board feet (actual) | Difference |
|---|---|---|---|---|
| 1×4 | 0.75 × 3.5 | 0.333 per ft | 0.219 per ft | −34% |
| 1×6 | 0.75 × 5.5 | 0.500 per ft | 0.344 per ft | −31% |
| 2×4 | 1.5 × 3.5 | 0.667 per ft | 0.438 per ft | −34% |
| 2×6 | 1.5 × 5.5 | 1.000 per ft | 0.688 per ft | −31% |
| 2×10 | 1.5 × 9.25 | 1.667 per ft | 1.156 per ft | −31% |
| 4×4 | 3.5 × 3.5 | 1.333 per ft | 1.021 per ft | −23% |
| 6×6 | 5.5 × 5.5 | 3.000 per ft | 2.521 per ft | −16% |
Common lumber sizes − board feet per foot
Use this table when you already know your linear footage and want a quick board-foot multiplier. All values are per running foot at the nominal size.
| Nominal | BF per ft (nominal) | BF per ft (actual) | Common use |
|---|---|---|---|
| 1×2 | 0.167 | 0.094 | Trim, lattice |
| 1×4 | 0.333 | 0.219 | Fascia, shelving, fencing |
| 1×6 | 0.500 | 0.344 | Deck boards, fence boards |
| 1×8 | 0.667 | 0.453 | Shelving, siding |
| 2×4 | 0.667 | 0.438 | Framing, studs, rails |
| 2×6 | 1.000 | 0.688 | Deck joists, rafters |
| 2×8 | 1.333 | 0.906 | Headers, joists |
| 2×10 | 1.667 | 1.156 | Floor joists, beams |
| 4×4 | 1.333 | 1.021 | Posts, fence posts |
| 6×6 | 3.000 | 2.521 | Heavy posts, beams |
Worked examples
| Project | Calculation | Board feet |
|---|---|---|
| 10 × 2×4×8 studs (nominal) | 10 × (2 × 4 × 96 ÷ 144) | 53.3 BF |
| 10 × 2×4×8 studs (actual) | 10 × (1.5 × 3.5 × 96 ÷ 144) | 35.0 BF |
| 20 × 1×6×8 fence boards (nominal) | 20 × (1 × 6 × 96 ÷ 144) | 80.0 BF |
| 20 × 1×6×8 fence boards (actual) | 20 × (0.75 × 5.5 × 96 ÷ 144) | 55.0 BF |
| 4 × 6×6×10 fence posts (nominal) | 4 × (6 × 6 × 120 ÷ 144) | 120.0 BF |
Notice the pattern: actual board feet run 20–35% below nominal for most dressed lumber. If you price a deck or fence using actual dimensions, you will under-order lumber by that margin − which is why the trade standard is nominal.
Common project quantities
Quick reference for typical residential projects. Board feet are nominal unless stated otherwise.
| Project | Per 100 sq ft or 100 ft | Typical lumber |
|---|---|---|
| Deck framing (16" o.c.) | ~2.2 BF per sq ft | 2×8 joists, 2×10 beams |
| Deck boards (5.5" wide, 1/8" gap) | ~2.4 BF per sq ft | 5/4×6 or 1×6 boards |
| Wood privacy fence | ~5 BF per linear ft | 1×6 boards, 2×4 rails, 4×4 posts |
| Wall framing studs (16" o.c.) | ~1.0 BF per sq ft of wall | 2×4 studs at 8 ft |
| Basic shelving | ~1 BF per linear ft of shelf | 1×8 or 1×10 boards |
Frequently asked questions
How do I calculate board feet?
How many board feet is a 2×4×8?
Is a 2×4 actually 2 inches by 4 inches?
What is the difference between board feet and linear feet?
How much does a board foot of lumber cost?
How much waste should I add for lumber?
How do I convert linear feet to board feet?
What is a board foot vs square foot vs linear foot?
Standards and sources
Board-foot formulas and dimensional lumber conventions are drawn from industry standards and published lumber estimation references. Key references:
- Board foot definition − 1 inch thick × 12 inches wide × 12 inches long = 144 cubic inches.
- US softwood lumber standard sizes for nominal vs actual dimensions (per National Lumber Grades Authority and grading rules).
- Waste factor guidance from trade estimating references − 5–10% framing, 10–15% decking, 15–20% mitered work.
- Typical 2026 US lumber prices from published price indices and retail lumber yard pricing.
Related guides
Go deeper on the questions behind this calculator.
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Estimates only. Confirm board dimensions, grade, and pricing with your lumber yard before ordering. Board-foot conventions vary by region and supplier. Last reviewed October 2026.