A board foot is 144 cubic inches of lumber — equivalent to a plank 1 inch thick, 12 inches wide, and 12 inches long. Lumber yards price hardwood by the board foot, so knowing the total BF for a project determines the budget. Enter thickness, width, and length in inches along with the number of pieces, and the calculator returns total board feet. Add a per-BF price to get a cost estimate.
The Board Foot Formula
Board feet = (Thickness × Width × Length) / 144, where all measurements are in inches. A 2″ × 6″ × 96″ board is (2 × 6 × 96) / 144 = 8 board feet. When buying multiple identical boards, multiply the single-board result by the quantity. Lumber yards use rough-sawn (actual) dimensions, not the nominal sizes stamped on construction lumber — a nominal 2×4 is actually 1.5″ × 3.5″.
Nominal vs. Actual Dimensions
Softwood from a home center is sold by nominal size: a '2×6' actually measures 1.5″ × 5.5″. Hardwood from a lumber yard is sold by rough-sawn actual dimensions, which is what the board foot formula expects. If you are pricing construction lumber (dimensional softwood), convert to actual dimensions first — otherwise the estimate will be too high.
Estimating Project Cost
Hardwood prices range from around $3/BF for poplar to $15+/BF for walnut or cherry. Enter the price per board foot for your species to get a material cost estimate. Remember to add 10–15% for waste from cuts, defects, and grain matching. For large projects, ask the yard for a volume discount — many offer price breaks above 100 BF.
Board Feet vs. Linear Feet
Linear feet measures length only and ignores thickness and width. A 10-foot 1×6 and a 10-foot 2×12 are both 10 linear feet, but the second board has four times the volume. Board feet accounts for all three dimensions, making it the standard unit for pricing hardwood. Construction lumber is sometimes sold by the linear foot because dimensions are standardized.
FAQ
Q: Do I use nominal or actual dimensions?
A: Use actual (measured) dimensions. For rough-sawn hardwood this is the true size. For dimensional softwood, a nominal 2×4 is actually 1.5″ × 3.5″ — enter the actual numbers for an accurate result.
Q: How much waste should I add?
A: Plan for 10–15% extra. Crosscuts, defects, and grain matching all consume material. Complex projects with angled joinery may need 20% or more.
Q: Why does my lumber yard quote differ from this calculator?
A: Yards may round up per board, apply minimum charges, or use slightly different measurement points. The calculator gives the mathematical result — the invoice may include rounding or surcharges.