Board Foot Calculator

The formula

Coverage and yield assumptions

Board feet are traditionally calculated from nominal dimensions for softwood framing (a 2×4 counts as 2 × 4 in) and from rough-sawn thickness for hardwoods, expressed in quarters: 4/4 = 1 in, 5/4 = 1.25 in, 8/4 = 2 in. The USDA Forest Products Laboratory's Wood Handbook describes these conventions. 1 board foot = 144 cu in = about 0.00236 m³.

Nominal vs actual sizes

A kiln-dried, surfaced 2×4 measures 1.5 × 3.5 in, a 1×6 is 0.75 × 5.5 in and a 4×4 is 3.5 × 3.5 in. Lumber yards price framing by the piece or linear foot, but when board feet are quoted for dimensional lumber they use nominal sizes. Hardwoods are sold rough by thickness in quarters; after planing, 4/4 stock ends up around 13/16 in thick.

Planning a woodworking project

Make a cut list of every part with its finished size. Add about 1 in to length and 1/4 in to width for each part to allow for squaring and defects, group parts that can come from one board, and total the board feet. Hardwood waste is often 20–30% once you remove knots, checks and sapwood you do not want, so the default 10% is a minimum.

Lumber grades

Hardwood grades such as FAS (firsts and seconds), Select and No. 1 Common describe the proportion of clear wood in a board. FAS gives long clear cuttings at a higher price; No. 1 Common is cheaper and fine for small parts. Softwood framing uses grades such as No. 2 and Stud.

Converting and buying

• Linear feet to board feet: linear feet × T × W ÷ 12.
• Ask whether prices are for rough or surfaced lumber.
• Let wood acclimate in your shop before final milling.

Common mistakes to avoid

• Mixing nominal and actual dimensions in one calculation.
• Forgetting to convert length to feet.
• Buying exactly the board feet in a cut list with no waste.
• Ignoring rough vs surfaced pricing.
• Using board feet for plywood or sheet goods.

Waste factor

10% is a minimum for framing and simple projects. Furniture and cabinetry from rough hardwood typically needs 20–30% because of defects, grain matching and milling losses.

Imperial and metric

Switch the toggle above the inputs to enter ft ↔ m, in ↔ cm. The page converts metric entries to imperial before calculating, using NIST factors (1 ft = 0.3048 m, 1 in = 2.54 cm), and shows key results in both systems.

Worked examples

Ten 2×6 × 8 ft boards at $4.50

Inputs: thickness 2 in; width 6 in; length 8 ft; number of pieces 10; waste factor 10%; cost per unit $4.5.

Result: Total: 88 board feet.

• Units to buy (rounded up): 88 board feet
• Per piece: 8 BF
• Volume: 0.208 m³
• Estimated material cost: $396.00

Walnut 8/4 × 8 in × 6 ft

Inputs: thickness 2 in; width 8 in; length 6 ft; number of pieces 4; waste factor 25%; cost per unit $14.

Result: Total: 40 board feet.

• Units to buy (rounded up): 40 board feet
• Per piece: 8 BF
• Volume: 0.094 m³
• Estimated material cost: $560.00

Oak 4/4 × 6 in × 8 ft

Inputs: thickness 1 in; width 6 in; length 8 ft; number of pieces 12; waste factor 20%.

Result: Total: 57.6 board feet.

• Units to buy (rounded up): 57.6 board feet
• Per piece: 4 BF
• Volume: 0.136 m³

Quick reference for common sizes

The table repeats the first worked example at smaller and larger sizes, keeping every other setting the same, so you can see how the board foot calculator result scales.

Limitations

Board feet measure volume, not usable yield. Prices vary by species, grade and thickness. Sheet goods like plywood are sold by the sheet, not board feet.