Board feet in practice
board feet = thickness × width × length (ft) ÷ 12 × quantity
For a typical 20 × 12 ft ledger deck frame — sixteen 2×8×12 joists, three 2×8×20 for the rim and ledger, two 2×10×20 beam plies and four 4×4×8 posts — that's about 445 board feet. The framing calculator fills this list in for you.
For deck boards themselves, the deck board calculator is more useful: it plans lengths and a cut list rather than board feet.
Frequently asked questions
How do you calculate board feet?
Board feet = nominal thickness (in) × nominal width (in) × length (ft) ÷ 12. A 2×8 that’s 12 ft long is 2 × 8 × 12 ÷ 12 = 16 board feet.
Why use nominal sizes instead of actual?
Board-foot pricing is based on nominal dimensions by convention, even though a 2×8 actually measures about 1-1/2" × 7-1/4". Use the sizes printed on the price tag.
Is lumber priced per board foot or per piece?
Home centers usually price framing lumber per piece; lumberyards and hardwood suppliers often quote per board foot or per thousand board feet. The calculator handles both.