Board Foot Calculator

The Board Foot Formula

Multiply thickness in inches by width in inches by length in feet, then divide by 12. A board that's 1 inch thick, 6 inches wide, and 8 feet long works out to 4 board feet. Hardwood dealers and specialty mills price this way because their stock comes in wildly inconsistent thicknesses and widths, unlike dimensional softwood framing lumber, which is milled to a handful of standard sizes.

Nominal Size vs. Actual Size Will Trip You Up

A rough-sawn '4/4' hardwood board is roughly 1 inch thick before drying and surfacing, but after it's been planed smooth on both faces (S2S), it typically finishes around 13/16 of an inch. Some mills bill board footage using the rough nominal size anyway, since that's what they cut the log to before any planing happens. Ask your supplier which convention they use before you assume this calculator's output matches their invoice exactly.

• Board feet is a volume measurement, not a length measurement, so a thick, narrow board can equal a thin, wide one.
• Framing lumber (2x4s, 2x6s, joists) is almost always priced per linear foot, not per board foot.
• Decking boards are typically sold per linear foot too, but composite and hardwood decking sometimes switch to board foot pricing for custom orders.
• Pricing pickets and rails for a wood fence works the same way, though most fence lumber is sold per linear foot; our fence cost calculator handles that side of the math.

Where Board Foot Pricing Shows Up Beyond Lumber Yards

Beyond raw hardwood boards, board foot pricing shows up in custom millwork quotes, live-edge slab sales, and reclaimed wood dealers, since all three deal in irregular, non-standard dimensions where a simple linear-foot price wouldn't fairly account for a wide slab versus a narrow one. If you're pricing a custom mantel, a butcher block countertop, or a set of stair treads cut from thick hardwood stock, expect the quote to reference board feet even if nobody explicitly explains the math behind it.

A Worked Example

Say you need ten pieces of walnut, each 5/4 (about 1.25 inches thick), 8 inches wide, and 6 feet long, for a set of shelves. Per piece: 1.25 x 8 x 6 = 60, divided by 12 = 5 board feet. Across ten pieces, that's 50 board feet total. At a hardwood price of $9 per board foot, quoted material cost before any waste allowance would run about $450, and most woodworkers still add 10% to 15% on top for cutting waste and defects.