Board feet.
Lumber volume in board feet (BF) with optional waste factor and unit pricing. Handles both nominal dimensional lumber (2×4, 2×6) and actual hardwood S4S (rough or surfaced) sizes.
How board feet work
A board foot (BF) is a volume of lumber equal to 144 cubic inches — i.e., 1 inch thick × 12 inches wide × 12 inches long, or any equivalent combination. The formula is:
BF = (thickness × width × length_in_inches) / 144 or equivalently: BF = (thickness × width × length_in_feet) / 12
Nominal vs actual dimensions
Construction-grade softwood lumber is sized by nominal dimensions, but the actual milled size is smaller. A "2×4" is really 1½″ × 3½″ after planing. Board-foot pricing uses the nominal dimensions by convention — even though you're getting less wood than the math suggests. This is a holdover from the days when rough green lumber was actually 2″ × 4″ and shrank during drying and planing.
Hardwood lumber is different: it's priced by actual dimensions, often in quarter-inch thicknesses (4/4, 5/4, 6/4, 8/4, etc.), where "4/4" means 1 inch thick (4 quarters = 1 inch).
Typical waste factors
| Use case | Waste factor | Why |
|---|---|---|
| Framing (straight cuts) | 5–10% | Simple cuts, defects rare in dimensional lumber |
| Decking | 10–15% | End-cuts and minor warping |
| Finish trim / casing | 15–20% | Miters, complex angles, defect culling |
| Cabinetmaking (hardwood) | 20–30% | Grain matching, defects in rough lumber, planing loss |
| Veneer / figured stock | 30–50% | Yield from rough boards is low when matching figure |
| Live-edge slabs | 20–40% | Drying checks, wane, sapwood |
Common pitfalls
- Always specify nominal vs actual. A "100 BF of 1×6 pine" means 100 BF using nominal 1″ × 6″ dimensions (the actual wood is ¾″ × 5½″). A "100 BF of 4/4 walnut" means 100 BF of wood that's actually 1″ thick. These cost very different amounts.
- Hardwood is sold by actual surface measurement. Rough hardwood ("rough sawn") is sold by actual measured dimensions. After surfacing on both sides ("S2S") it's about 1/16″ thinner; surfaced four sides ("S4S") it's ¾″ thick from a 4/4 rough board.
- Lineal feet ≠ board feet. "100 lineal feet of 2×4" is a length measurement. The board-foot equivalent is 100 ft × (2 × 4) / 12 = 66.67 BF.
- Plywood is sold by sheet, not by board foot. A 4×8 sheet of ¾″ plywood has 24 ft² of face area, or roughly 16 BF equivalent, but you'd never buy or price it that way.
- Board feet doesn't include defect culling. The waste factor on this calculator accounts for that. Hardwood specifically is graded (FAS, Selects, #1 Common, #2 Common) by yield — FAS gives ~83% clear face cuttings; #1 Common gives ~67%. If you're buying #1 Common for finish work, your effective yield is much lower than the BF count.
Sources
- Nominal dimensions: American Lumber Standard PS 20 — American Softwood Lumber Standard. Specifies the allowed deviation between nominal and actual dimensions.
- Hardwood sizing: NHLA (National Hardwood Lumber Association) Rules for the Measurement and Inspection of Hardwood and Cypress.
- Plywood sizing: APA — The Engineered Wood Association, Voluntary Product Standard PS 1.
Disclaimer. Board-foot calculations are nominal volumes for pricing and planning. Actual material needed for a project depends on cuts, grain matching, defect culling, and joinery — always order more than the bare math suggests.