Board Feet Calculator
Calculate lumber volume in board feet for any dimension
Common Lumber Sizes (Actual Dimensions)
| Nominal | Actual | BF per 8ft | BF per 12ft |
|---|---|---|---|
| 1×4 | 0.75" × 3.5" | 1.75 | 2.63 |
| 1×6 | 0.75" × 5.5" | 2.75 | 4.13 |
| 1×8 | 0.75" × 7.25" | 3.63 | 5.44 |
| 2×4 | 1.5" × 3.5" | 5.33 | 8.00 |
| 2×6 | 1.5" × 5.5" | 8.00 | 12.00 |
| 2×8 | 1.5" × 7.25" | 10.67 | 16.00 |
| 2×10 | 1.5" × 9.25" | 13.33 | 20.00 |
| 2×12 | 1.5" × 11.25" | 16.00 | 24.00 |
| 4×4 | 3.5" × 3.5" | 10.67 | 16.00 |
What Is a Board Foot?
A board foot is a unit of volume used exclusively in the North American lumber industry. One board foot equals a piece of wood 12 inches long, 12 inches wide, and 1 inch thick — or 144 cubic inches. It is how lumber is priced, traded, and discussed by woodworkers, contractors, and mills everywhere on the continent.
The formula is straightforward: thickness (inches) × width (inches) × length (feet) ÷ 12 = board feet. A 2-inch thick board that is 6 inches wide and 10 feet long contains 2 × 6 × 10 ÷ 12 = 10 board feet. Where it gets confusing for beginners is the distinction between nominal and actual dimensions.
Nominal vs Actual Dimensions
When you buy a "2×4" at the lumber yard, you are not getting a board that measures 2 inches by 4 inches. The actual dimensions are 1.5 inches by 3.5 inches. The nominal size refers to the rough-sawn dimension before the lumber was dried and planed smooth. This discrepancy matters significantly when calculating board feet — using nominal dimensions overestimates your material by 10-20% depending on the size.
Hardwood lumber sold at specialty suppliers follows different conventions. Rough-sawn hardwood is sold by actual thickness in quarter-inch increments: 4/4 (four-quarter) is 1 inch thick, 5/4 is 1.25 inches, 6/4 is 1.5 inches, 8/4 is 2 inches. These are actual rough dimensions before planing. When you surface a 4/4 board, you lose about 3/16 inch per face, leaving approximately 13/16 inch of finished thickness.
Pricing Lumber by the Board Foot
Softwood framing lumber (pine, spruce, fir) at home centers is typically priced per linear foot or per piece. But hardwoods and specialty woods are almost always priced per board foot. Red oak runs $4-8 per board foot, walnut $8-14, cherry $6-10, and maple $5-9. Exotic species like purpleheart or padauk can exceed $15 per board foot.
When buying hardwood, always calculate your board footage before visiting the supplier and add 15-25% for waste. Rough lumber has defects, sapwood sections you may not want, and cutting waste that adds up faster than most beginners expect. A project requiring 20 board feet of finished walnut means buying 24-25 board feet of rough stock.
Waste Factor by Project Type
The amount of waste varies dramatically by what you are building. Furniture projects with many small parts generate more cutoff waste — plan for 25-30% extra. Shelving and large panels are more efficient at 15-20%. Turning blanks and small craft items can waste 40-50% of the original board. If you are buying expensive wood, sketch a cutting diagram on paper first to minimize waste and identify whether you can get all your parts from the boards available.
How do I calculate board feet?
Thickness (inches) × width (inches) × length (feet) ÷ 12. A board that is 1 inch thick, 8 inches wide, and 6 feet long: 1 × 8 × 6 ÷ 12 = 4 board feet. Use actual dimensions rather than nominal for accuracy.
Should I use nominal or actual dimensions?
For purchasing dimensional lumber at a home center: nominal is fine since pricing is per piece. For hardwood from a specialty supplier: actual dimensions matter because you are paying per board foot. For project planning: always use actual dimensions so your joinery fits.
How much extra should I buy for waste?
15-20% for straightforward projects like shelves. 25-30% for furniture with many small parts. 30-40% for complex projects or wood with significant defects. When in doubt, round up — having extra wood is always better than making a second trip to the lumber yard.