Board Feet Calculator
How many board feet is that lumber — and what does it cost?
How this is calculated
- Board feet = (thickness in × width in × length ft) ÷ 12
- Total = per-board bf × quantity
- Cost = total bf × price per bf
Common questions
How many board feet is a 2x4x8?
2 × 4 × 8 ÷ 12 = 5.33 board feet. Note that uses the NOMINAL dimensions — lumber math always works in nominal sizes, even though a 2x4 actually measures 1.5 × 3.5.
Why is hardwood sold by the board foot?
A board foot is a volume unit (144 cu in) that works for any combination of thickness, width, and length — so a 12 ft long 1×12 and a 6 ft long 2×12 both cost the same per bf. Sawmills, wholesalers, and lumberyards all speak it, which makes price comparison possible across wildly different board shapes.
Do I use nominal or actual dimensions?
Nominal. A "2×6" is really 1.5 × 5.5, but board-foot pricing uses the nominal 2 × 6 — the sawmill rough-cut size the convention was built on. The one exception: hardwoods sold in quarters (4/4, 5/4, 8/4) are close to actual rough thickness.
How much waste should I add for a woodworking project?
20-30% over the measured total for furniture projects — hardwood grading (FAS, Select, #1 Common) allows some defects, and grain matching eats wood. Buy the longest/widest boards you can transport; fewer pieces = fewer seams to work around.
What does S4S or S2S mean in lumber listings?
Surfaced on 4 sides (S4S) = planed smooth, ready to use, priced higher. Rough-sawn (S2S or S3S) is cheaper per bf but needs jointing/planing — worth it if you own the machines or want specific final thickness. Board-foot math is the same either way.