Board Feet Calculator

Board feet (BF) is the standard North American unit for measuring and pricing lumber volume.
One board foot is a piece of wood 1 foot long, 1 foot wide and 1 inch thick, or any other shape with the same volume.

Board feet formula: Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12

Or equivalently, with length in inches: Board Feet = (Thickness × Width × Length) ÷ 144

Variable definitions:

• Thickness: measured in inches (use nominal thickness for rough lumber; actual thickness for S4S dressed lumber)
• Width: measured in inches
• Length: measured in feet (or divide inches by 12)
• Dividing by 12: converts the inch-based area to a per-foot-of-length volume unit

Nominal versus actual dimensions. This is the distinction that costs people money.
Lumber is sold under a nominal (name) size, but the dressed board is smaller:

• “1×4” = 0.75″ × 3.5″ actual
• “2×4” = 1.5″ × 3.5″ actual
• “2×6” = 1.5″ × 5.5″ actual
• “2×8” = 1.5″ × 7.25″ actual
• “4×4” = 3.5″ × 3.5″ actual

Board feet calculations for pricing use nominal dimensions; structural calculations use actual dimensions.

Price from board feet: Total Cost = Board Feet × Price per Board Foot

Rough-sawn hardwood pricing (US average):

• Pine: $2–$4/BF
• Oak: $5–$9/BF
• Walnut: $10–$18/BF
• Cherry: $8–$14/BF
• Maple: $6–$10/BF
• Exotic (teak, mahogany): $15–$40/BF

Waste factor: add 10 to 20% for kerf loss, defects and miscuts. There is a waste box above so this ends up in the total rather than being something you are supposed to remember at the till. Rough-sawn stock with live edges and knots wants the top of that range; clean S4S stock for simple cuts can sit at the bottom.

Worked example: You need to build shelves using 1×8 oak boards (nominal). You require 5 pieces, each 8 feet long.

• Board feet per piece: (1 × 8 × 8) ÷ 12 = 5.33 BF
• Total board feet: 5 × 5.33 = 26.67 BF
• Add 15% waste: 26.67 × 1.15 = 30.67 BF (buy 31 BF)
• Cost at $7/BF: 31 × $7 = $217

Linear feet conversion: For framing lumber where length (not volume) matters: 1 linear foot of 2×4 = (2 × 4 × 1) ÷ 12 = 0.667 BF.