Question 1

What is a board foot in lumber?

Accepted Answer

A board foot is a volume measurement equal to 144 cubic inches (12in x 12in x 1in). The formula is: board feet = (thickness in × width in × length ft) / 12. Board feet are used to price hardwood and larger dimensional lumber.

Question 2

Why is a 2x4 actually 1.5 x 3.5 inches?

Accepted Answer

Dimensional lumber is sized by its rough-sawn dimensions before drying and planing. After surfacing, a 2x4 shrinks to 1.5 x 3.5 inches. Always use actual (surfaced) dimensions for board foot calculations of dimensional lumber.

Question 3

How do I convert linear feet to board feet?

Accepted Answer

Linear feet only counts length. To convert to board feet, multiply linear feet by the cross-section area in square feet. For a 2x4 (1.5 x 3.5 in = 5.25 sq in = 0.0365 sq ft), one linear foot = 0.0365 board feet.

Question 4

How much extra lumber should I buy?

Accepted Answer

Add 10-15% extra to your order for cuts, mistakes, defects and future repairs. For framing projects, 15% is standard. For fine woodworking with selective grain, 20% is safer.