Lumber Calculator

What Is a Board Foot?

A board foot (bd ft) is a unit of lumber volume, not area. One board foot = 144 in³. A 2 × 4 that is 8 ft long is not actually 2 in × 4 in (it is surfaced to about 1.5 × 3.5), but board-foot math uses the nominal dimensions unless you enter actuals.

Why Use Board Feet?

Hardwood is sold by the board foot, while softwood dimensional lumber is usually sold by the piece or linear foot. Knowing both lets you convert between pricing methods and avoid surprises at the yard.

Nominal vs actual dimensions

A "2 × 4" is surfaced to about 1.5 × 3.5 in, and a "1 × 6" to about 0.75 × 5.5 in. Board-foot pricing at the yard, however, uses the nominal 2 × 4 or 1 × 6 — the rough-sawn size before planing. That means a board-foot count can overstate the finished volume you actually get. Enter nominal sizes when matching yard quotes, and actual sizes when you need the true volume of the wood you will cut.

Worked Example 1: A 2 × 4, 8 ft Long

Board feet each = (2 × 4 × 8) / 12 = 64 / 12 ≈ 5.33 bd ft. Ten pieces = 53.33 bd ft. Linear feet = 80 ft.

Worked Example 2: A 1 × 6, 10 ft Long

Board feet each = (1 × 6 × 10) / 12 = 60 / 12 = 5.00 bd ft. Linear feet = 10 ft each.

Edge Cases

• Zero dimension → no result.
• Quantity 1 default if blank.
• Actual vs nominal: enter actual sizes for surfaced lumber to get true volume.
• Very long boards scale linearly with length.
• Mixed sizes: compute each size separately and sum.

Worked Example 3: A Hardwood Table Top

A table top needs 5 boards, each 1 × 6 (actual 0.75 × 5.5 in) and 6 ft long. Board feet each = (1 × 6 × 6) / 12 = 3 bd ft. Total = 15 bd ft. At a yard price of $6 per board foot, the raw stock is about $90 before waste.

Worked Example 4: Estimating With a Waste Factor

The same 15 bd ft, planned with a 1.5× waste factor for grain selection and mistakes, means buying about 22–23 bd ft. Woodworkers rarely buy the exact net footage because boards vary in width and you cut around defects.

Converting price per board foot to per piece

If a 2 × 4 × 8 costs $4 and contains 5.33 bd ft, that is about $0.75 per board foot. Comparing that to a hardwood at $6 per board foot shows why species choice dominates cost far more than dimensions.

Worked Example 5: A 2 × 10 Floor Joist Takeoff

A 24 ft span needs 2 × 10 joists at 16 in centers across a 12 ft width. Joists: 12 / 1.333 + 1 = 10, each 24 ft, so 240 linear ft. Board feet each = (2 × 10 × 24) / 12 = 40 bd ft; total = 400 bd ft. At a $1.10 per board foot framing price that is about $440 in joist stock before waste.

Worked Example 6: Comparing Two Widths for a Shelf

A shelf needs 8 ft of 1 × 10 versus 1 × 12, five boards each. 1 × 10: (1 × 10 × 8) / 12 = 6.67 bd ft each, 33.3 total. 1 × 12: (1 × 12 × 8) / 12 = 8.0 bd ft each, 40 total. The wider board costs 20% more in board feet for 20% more width — the ratio is the same, so choose width by the project, not by hoped-for savings.

Worked Example 7: A 2 × 6 Deck Rim at 20 ft

A deck rim board 2 × 6 × 20 ft: board feet = (2 × 6 × 20) / 12 = 20 bd ft each. Two rims (both sides) = 40 bd ft. At a $1.10 framing price that is $44 in rim stock; add the 10 × 8 ft joists computed earlier and the ledger for a full framing takeoff.

Worked Example 8: A Workbench Top of 2 × 12s

A bench top 30 in deep and 6 ft long built from 2 × 12 boards laid flat: each board is 1 ft wide, so six boards cover 30 in. Each 2 × 12 × 6 ft = (2 × 12 × 6) / 12 = 12 bd ft, six boards = 72 bd ft. Flat-laid 2 × 12s make a thick, stable top but use far more board feet than a glued panel of 1 × 6s would.

Worked Example 9: A Fence of 1 × 6 Pickets

A 40 ft fence with 1 × 6 pickets at 5.5 in actual width, spaced with a 0.5 in gap, covers 6 in per picket: 40 × 12 / 6 = 80 pickets. Each 1 × 6 × 6 ft = 3 bd ft, total 240 bd ft. Add the 2 × 4 rails and posts separately; the picket count drives the bulk of the board feet on a long run.

Quarter-sawn vs plain-sawn volume

The board-foot count is identical regardless of how the log was sawn; only price and stability differ. Quarter-sawn stock costs more per board foot but moves less with humidity, which matters for tabletops and instrument parts. Buy the footage the same way, just budget more per unit.

Estimating a wall of studs

A 20 ft wall at 16 in centers needs 20 / 1.333 + 1 = 16 studs, each 8 ft (for a standard 8 ft wall) = 128 linear ft. At 2 × 4 dimensions that is 128 × 5.33 / 10 ≈ 68 bd ft of framing. Add plates (top and bottom 2 × 4 runners along the wall) and a 10–15% waste factor for cuts and culls.

What is a board foot?

A board foot is 144 cubic inches: a 1 in × 12 in × 12 in volume of lumber.

How do I calculate board feet?

Multiply thickness (in) × width (in) × length (ft), then divide by 12. Multiply by quantity for the total.

Is a 2x4 really 2 by 4 inches?

No. Dimensional lumber is surfaced to about 1.5 × 3.5 in, but board-foot pricing usually uses nominal 2 × 4.

How many board feet in a 2x4x8?

(2 × 4 × 8) / 12 ≈ 5.33 board feet.

What is linear feet?

Length times quantity, ignoring width and thickness. Useful for pricing by the foot.

Should I use actual or nominal dimensions?

Use nominal for supplier pricing; use actual for true volume of finished material.

How much extra lumber should I buy?

About 10-15% for cuts, defects, and errors.

Can I calculate hardwood flooring?

Yes — multiply board feet by price per board foot, or convert to square feet using width × length.

Does length affect board feet linearly?

Yes, doubling the length doubles the board feet for a fixed cross-section.

Is board foot the same as square foot?

No. Board feet measure volume; square feet measure area. A board's square footage is width × length.

Why does a 2×4 cost more than its board feet suggest?

Retail softwood is priced per piece, not per board foot, and includes milling, grading, and handling. The board-foot figure is a volume check, not the shelf price.

Can I estimate plywood with this?

Plywood is sold by the sheet (e.g., 4 × 8 ft = 32 ft²), not by board foot. Use a square-foot estimate for sheet goods and reserve board feet for solid lumber.

What does "4/4" or "8/4" mean?

Those are quarter-inch thickness names: 4/4 ≈ 1 in rough, 8/4 ≈ 2 in rough. Use the rough thickness in the board-foot formula even though the planed board will be thinner.

How do I estimate a project with many parts?

Make a parts list, compute board feet for each part, sum by thickness, then apply a 1.5–2× waste factor. That is the footage to buy, not the net footage of the finished parts.

Does moisture content change board feet?

Green lumber shrinks as it dries, so buy slightly more if you start from unseasoned stock. The volume math is the same; the usable yield is lower.

How do I convert board feet to square feet?

For a board of known width W (in) and length L (ft), square feet = (W / 12) × L. Board feet = square feet × thickness (in). Use square feet when comparing to sheet goods and board feet when pricing solid stock.

What is the difference between surfaced and rough lumber?

Rough lumber is the full nominal size; surfaced (S4S) lumber is planed smaller. A rough 2 × 4 is a full 2 × 4 in, while surfaced is 1.5 × 3.5 in. Yard board-foot pricing usually uses nominal; enter actuals only when you need true cut volume.

Can I estimate trim and molding with this?

Yes — molding is sold by linear foot, so use the linear-feet output and ignore board feet for pricing. For the volume of a solid wood molding blank, enter its actual cross-section and length.

How many boards come in a bundle?

Softwood dimensional lumber is often bundled in units (e.g., 294 ft of 2 × 4 × 8 per unit). Divide your linear feet by the per-unit count to estimate bundles, or just use board feet if the yard prices by the foot.

How do I estimate a roof of rafters?

A gable roof's rafters run from the wall plate to the ridge. A 24 ft wide house with a 6/12 pitch has a run of 12 ft and a rafter length of 12 / cos(26.6°) ≈ 13.4 ft; order 2 × 8 × 14 ft rafters at 24 in centers. Board feet each = (2 × 8 × 14) / 12 ≈ 18.7 bd ft; a 24 ft wall needs 13 rafters, about 243 bd ft total before waste.

What about stair stringers and treads?

A straight stair with 16 steps needs one 2 × 12 stringer per side plus a middle one for width. Each stringer 16.4 ft long is 2 × 12 × 16.4 / 12 ≈ 32.8 bd ft; three stringers ≈ 98 bd ft. Treads are separate 2 × 6 or 2 × 12 stock counted by the same formula, so total the stringers and treads as distinct line items.

Can I estimate a timber-frame brace?

Heavy timbers are 4 × 4, 6 × 6, or larger and use the same board-foot formula with their rough dimensions. A 6 × 6 × 8 ft post is (6 × 6 × 8) / 12 = 24 bd ft; a frame of eight posts is 192 bd ft before waste. Because timbers are priced by the board foot, the count is exactly what the yard will quote.

How do I handle a project with mixed species?

Compute board feet for each species separately, because the price per board foot differs by wood. A maple top and a pine base may share dimensions but not cost, so keep two totals and apply waste to each. The linear feet are still summed for transport planning regardless of species.

Does buying rough-sawn save money?

Rough stock is cheaper per board foot but larger in nominal size, so you pay for wood you plane away. A rough 2 × 4 is a full 2 × 4 while a surfaced one is 1.5 × 3.5; enter rough dimensions and you will see a higher board-foot figure that reflects the true volume before milling.

How do I estimate trim and crown molding takeoff?

Crown and base are sold by linear foot, so use the linear-feet output and ignore board feet for pricing. For the solid-wood blank behind a profiled molding, enter its actual cross-section and length; a 3/4 × 3 in blank at 10 ft is (0.75 × 3 × 10) / 12 = 1.875 bd ft each, summed over the room's perimeter.