Board Feet Calculator
Board feet and cubic volume of lumber from nominal dimensions and quantity.
Quick answer
- Board feet = (thickness in inches × width in inches × length in feet) ÷ 12 — a nominal 2×4, 8 ft long, is 5.33 board feet.
- Board feet are tallied on nominal (rough) dimensions, not the surfaced size: that same 2×4 actually measures 1.5 × 3.5 in, which would be only 3.5 board feet at its finished size.
- Project cost = total board feet × price per board foot; add 15–25% for milling waste, defects and grain matching on woodworking projects.
- Worked example — Board feet per piece: 5.333 bf (full example below).
Board Feet Calculator
| Board feet per piece | 5.333 bf |
| Total board feet | 5.33 bf |
| Total volume | 0.444 cu ft |
A single 2×4 that is 8 ft long contains (2 × 4 × 8) ÷ 12 = 5.33 board feet, about 0.444 cu ft of wood.
Hardwood and rough lumber are priced by the board foot: a volume equal to a board 1 inch thick, 12 inches wide and 1 foot long (144 cubic inches). Enter the thickness and width in inches, the length in feet, and how many pieces you need.
The result also shows cubic feet (board feet ÷ 12), which helps when comparing against timber priced by volume. Note that board-foot counts use nominal dimensions at the lumberyard — a rough-sawn 2×4 sold as 8 board feet per 8 ft length is counted at its full nominal size even though the finished board measures less.
The formula
Worked example
A single 2×4 that is 8 ft long contains (2 × 4 × 8) ÷ 12 = 5.33 board feet, about 0.444 cu ft of wood.
The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.
Nominal vs actual lumber sizes
| Nominal size | Actual size (in) | Board feet per 8 ft piece (at nominal size) |
|---|---|---|
| 1×4 | 0.75 × 3.5 | 2.67 |
| 2×4 | 1.5 × 3.5 | 5.33 |
| 2×6 | 1.5 × 5.5 | 8 |
| 2×8 | 1.5 × 7.25 | 10.67 |
| 4×4 | 3.5 × 3.5 | 10.67 |
| 1×6 | 0.75 × 5.5 | 4 |
Actual sizes are the standard surfaced dimensions for softwood lumber. Board-feet figures are this calculator's outputs at the nominal dimensions — the basis lumberyards tally and bill on.
When this estimate may be wrong
- Board feet use nominal dimensions — the rough blank before surfacing — so the tally is higher than the finished board's measured volume. That is the industry convention, not an error.
- Hardwood and rough stock may be tallied at the pre-surfacing thickness (for example 4/4 stock at a full 1 in nominal), and yards vary slightly in how they round lengths.
- Milling waste and moisture movement are not included — add your waste allowance separately when pricing a project.
Frequently asked questions
What is a board foot?
A unit of lumber volume: 144 cubic inches, visualized as a 1 in × 12 in × 1 ft board. Lumberyards tally rough and hardwood stock in board feet regardless of the board's actual shape.
Why does the yard's tally differ from the finished size?
Board feet are calculated from nominal (rough) dimensions before surfacing. A surfaced '2×4' actually measures 1.5 × 3.5 in, but it is sold by the board footage of the rough blank it came from.
How do I price a project in board feet?
Total board feet × price per board foot. Add 15–25% extra for a woodworking project to cover milling waste, defects and grain matching — more for rough stock.
Category: Construction & Home calculators
Sources & methodology
Per-piece board feet = (thickness × width × length in feet) ÷ 12, using the entered dimensions; totals multiply by quantity, and cubic feet = board feet ÷ 12.
Content last reviewed by CalcHub Editorial.
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