Board Foot Calculator
Board feet and cost from nominal dimensions — the way the lumber trade actually tallies.
Your boards (nominal sizes)
Materials list
Generated by AllUnits.io — allunits.io/calculators/board-feet
How this calculator figures it
One board foot is the volume of a board 1 inch thick and 12 inches square: (thickness × width × length in feet) ÷ 12, computed on nominal dimensions per trade convention under the American Softwood Lumber Standard (NIST PS 20). Actual dressed sizes are smaller — a nominal 2×4 measures 1.5 × 3.5 inches — but pricing and tallying stay nominal.
How it works
A 2×4×8 ft is 2 × 4 × 8 ÷ 12 = 5.33 board feet — even though it measures 1.5 × 3.5 inches dressed. Some online calculators use actual dimensions here; that is wrong by trade convention. With a price entered, cost is simply board feet × price: at $4.20 per board foot, that 2×4×8 runs 5.33 × 4.20 ≈ $22.40.
Nominal vs actual sizes (NIST PS 20)
| Nominal | Actual (dry, dressed) |
|---|---|
| 1×4 | 3/4" × 3.5" |
| 1×6 | 3/4" × 5.5" |
| 2×4 | 1.5" × 3.5" |
| 2×6 | 1.5" × 5.5" |
| 2×12 | 1.5" × 11.25" |
| 4×4 | 3.5" × 3.5" |
| 6×6 | 5.5" × 5.5" |
| 5/4×6 deck board | 1" × 5.5" |
Board foot FAQs
Why nominal and not actual size?
Board-foot measure predates surfacing; the lumber trade prices on nominal dimensions per the American Softwood Lumber Standard, PS 20.
How many board feet in a 2×4×8?
5.33 board feet: 2 × 4 × 8 ÷ 12.
What does 4/4 mean?
Hardwood thickness in quarters of an inch — 4/4 is 1 inch nominal, 5/4 is 1.25 inches, 8/4 is 2 inches.
Board feet vs linear feet?
Board feet measure volume; linear feet just length. Dimensional construction lumber is sold by the stick; hardwood by the board foot.
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Related calculators & sources
Decking projects: the Deck Board Calculator counts boards and screws, and the Stair Calculator lays out stringers from 2×12 stock. Framing a wall: Wall Framing Calculator. Nominal-to-actual sizes come from NIST PS 20; convert measurements with the length converter.
Estimates for planning and purchasing. Not engineering or code-compliance advice — confirm structural work with your local building department.