Lumber Calculator
Calculate board feet and linear feet for your lumber purchases.
What are board feet and how do I calculate them?
Board foot (BF) is lumber volume measurement: 1 BF = 144 cubic inches (1"x12"x12" or 2"x6"x12"). Formula: (Thickness x Width x Length in inches) / 144. Example: 2x4x8 = (2 x 4 x 96) / 144 = 5.33 board feet. Lumber sold by BF for hardwoods (oak, walnut), by piece for construction grade. Prices listed per board foot ($3-15/BF depending on species). Understand BF to compare prices and order correctly.
What do lumber dimensions like 2x4 actually mean?
Nominal vs actual sizes (dried/planed): 2x4 = actually 1.5"x3.5", 2x6 = 1.5"x5.5", 2x8 = 1.5"x7.25", 2x10 = 1.5"x9.25", 2x12 = 1.5"x11.25", 4x4 = 3.5"x3.5", 6x6 = 5.5"x5.5". Lumber shrinks during drying and is planed smooth. Always use actual dimensions for calculations. Lengths are true: 8' board is 96" long. Frustrating but industry standard since 1964.
How many 2x4 studs do I need for a wall?
Standard framing: 16" on-center spacing. Formula: (Wall Length in inches / 16) + 1. Example: 12' wall = 144" / 16 = 9 studs + 1 = 10 studs. Also need: Top plate (2 boards), bottom plate (1 board), corners (extra studs), headers (2x6 or larger over doors/windows), cripples/jack studs at openings. 8' wall needs 8' studs (92-5/8" precut for 8' walls), taller walls need longer. Add 10-15% waste for cuts and mistakes.
What grade of lumber should I buy?
Construction grades (softwood): Stud grade: Framing, non-load bearing, economical. #2 or better: Structural, most common, some knots allowed. #1: Fewer knots, stronger, pricier. Select/Premium: Furniture, visible projects, expensive. Pressure-treated: Outdoor/ground contact (decks, fences). For framing: Stud grade or #2 fine. For furniture/finish: Select or premium. For outdoor: PT rated for ground contact. Higher grades waste money on hidden structural lumber.