How to Calculate Board Feet and Convert Linear Feet

Board feet measure lumber volume. Linear feet measure length. Start with thickness, width and length to calculate a board-foot quantity, then use the same dimensions when comparing prices or converting back to linear feet.

By CalcsteadUpdated September 23, 20266 min read

The short answer

Board feet = thickness (in) × width (in) × length (ft) × piece count ÷ 12. For twelve true 1 × 6 in boards, each 8 ft long, the result is 48 board feet and 96 linear feet. If every dimension is in inches, divide by 144 instead.

Use the board feet calculator

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Calculate your board feet

Enter one group of boards with the same dimensions. Add separate groups in the full calculator.

Thickness (in)Width (in)Length per board (ft)Number of boards (pieces)

Board feet48 BF

Total linear feet96 ft

Wood volume4 ft³

These are geometric quantities before allowance. To check a quote, use the dimensions and billing basis agreed with the supplier.

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How to calculate board feet, step by step

Write down the thickness and width in inches, the length in feet, and the number of identical pieces. Multiply the four numbers, then divide by 12. A board foot is the volume of a 12 × 12 × 1 inch piece: 144 cubic inches, or one-twelfth of a cubic foot.

The divisor follows the units. With length in feet, thickness × width × length ÷ 12 gives board feet. With all three dimensions in inches, divide their product by 144. For a true 1 × 6 × 96 inch board, 576 ÷ 144 = 4 board feet, the same as 1 × 6 × 8 ÷ 12.

Choose physical dimensions for geometric volume, or the agreed billing dimensions for a quote.
Calculate each set of identical pieces together.
Add the sets before applying an optional purchase allowance.
Keep enough precision until the final stock or invoice rounding.

Three units that answer different questions

Linear feet describe how far a board runs, regardless of its width or thickness. Square feet describe a face or surface. Board feet include all three dimensions and describe volume. An 8-foot piece is 8 linear feet whether it is narrow trim or a wide plank.

Example: a true 1 × 6 in board, 8 ft long

Dimensions in this example are specified physical dimensions. Supplier billing conventions can use a different basis.

Measurement	Calculation	Quantity
Linear feet	Length	8 linear ft
Face area	6 ÷ 12 × 8	4 ft²
Board feet	1 × 6 × 8 ÷ 12	4 board ft

Convert linear feet to board feet

Board feet = thickness in inches × width in inches × total linear feet ÷ 12. For identical boards, calculate total linear feet as piece count × length of each piece. If cross-sections differ, calculate each group separately before adding board feet.

The inverse is linear feet = board feet × 12 ÷ (thickness × width). This conversion is valid only for the stated cross-section. Ten board feet does not determine a unique length when the width or thickness is unknown.

Eight-foot boards with different cross-sections

Each row uses the exact dimensions shown; the table does not infer a sales size from a nominal label.

Thickness × width	Linear feet	Geometric board feet
1 × 6 in	8	4
2 × 6 in	8	8
0.75 × 5.5 in	8	2.75
1.5 × 5.5 in	8	5.5

Worked example: comparing two lumber quotes

Suppose a project needs twelve boards, each a true 1 inch thick, 6 inches wide and 8 feet long. Total length is 12 × 8 = 96 linear feet. Volume is 1 × 6 × 96 ÷ 12 = 48 board feet.

At an invented $6 per board foot, the material total is $288. At an invented $3 per linear foot for those same dimensions, it is also $288. The prices are equivalent because each linear foot contains 0.5 board feet. At 2 inches thick and the same width, that relationship would change.

Compare equivalent species, grade, moisture condition, dimensions and milling services too. Converting units cannot make two different products interchangeable, and these demonstration prices are not market quotes.

How many board feet are in a 2×4×8?

Using the named 2 × 4 inch cross-section and an 8-foot length gives 5⅓ board feet. Using a measured 1.5 × 3.5 inch cross-section gives 3.5 geometric board feet. NIST explains why the nominal two-by-four name differs from its finished dimensions. Neither calculation alone tells you how a supplier must bill a particular product.

Named dimensions versus an example measured cross-section

The measured columns are explicit example inputs. Check your stock and the supplier’s billing rules; the label alone is not a measurement.

Board label	Named-size calculation	Measured dimensions used	Geometric BF
2×4×8	2 × 4 × 8 ÷ 12 = 5.333 BF	1.5 × 3.5 in, 8 ft	3.5
2×4×10	2 × 4 × 10 ÷ 12 = 6.667 BF	1.5 × 3.5 in, 10 ft	4.375
2×6×10	2 × 6 × 10 ÷ 12 = 10 BF	1.5 × 5.5 in, 10 ft	6.875

Add a mixed lumber order

Suppose a cut list calls for twelve true 1 × 6 inch boards at 8 feet and six true 1 × 8 inch boards at 10 feet. The first group contains 48 board feet. The second contains 1 × 8 × 10 × 6 ÷ 12 = 40 board feet. Together they contain 88 board feet.

An example 10% allowance gives 88 × 1.10 = 96.8 board feet. That is a volume target, not a promise that an arbitrary bundle will yield the parts. If pieces have different prices per board foot, price each group separately before adding the costs.

Physical dimensions and invoice dimensions can differ

A nominal size is a product label, so it is not automatically the correct physical cross-section. Dressed lumber may measure less than its label suggests. Rough stock, surfaced stock and board-foot billing may follow different conventions.

For geometric volume, enter the dimensions you actually intend to measure. To reproduce an invoice, ask the supplier which thickness, width, length and rounding rules it bills. Do not automatically replace a quoted billing dimension with a tape measurement and assume the invoice is wrong.

Volume does not replace a cutting plan

A requirement for 48 board feet does not guarantee that any 48-board-foot bundle can yield the required parts. Board lengths, widths, defects, joint positions and saw cuts still matter. Keep a cut list with piece counts and minimum usable dimensions.

For decking, surface coverage also depends on the finished board width, gap and layout. Use the deck-board calculator for rows and stock pieces; use board feet when the purchase or comparison actually calls for lumber volume.

Group boards by cross-section before converting length to volume.
Check whether the supplier quotes per piece, linear foot or board foot.
Round the actual stock pieces needed for the cutting plan.
Keep optional surplus separate from the base takeoff.

Common questions

Is one board foot the same as one square foot?

Only when the wood is exactly 1 inch thick. At that thickness, one square foot of face area contains one board foot. A 2-inch-thick board has twice that volume for the same face area.

Can I convert a board-foot price to a linear-foot price?

Yes, for known dimensions on the same billing basis. Price per linear foot = price per board foot × thickness in inches × width in inches ÷ 12.

Why do some board-foot formulas divide by 144?

They use length, width and thickness all in inches. One board foot is 144 cubic inches. When length is in feet and the cross-section is in inches, divide by 12 instead.

How many linear feet are in 10 board feet?

At a true 1 × 6 inch cross-section, 10 × 12 ÷ (1 × 6) = 20 linear feet. At 2 × 6 inches, the same volume is 10 linear feet. You need both cross-section dimensions to convert.

Sources and product references

Mississippi State University Extension — Measuring Standing Sawtimber
Defines the board foot and the length × width × thickness calculation. Our lumber examples are dimensional arithmetic, not log-yield predictions.
NIST — SI units: volume
Reference for volume units. Coverage tables and worked examples on this page are Calcstead calculations, not product performance guarantees.
NIST — Making Sure that Lumber Measures Up
Explains nominal versus actual lumber dimensions, including the two-by-four example. Checked September 23, 2026.

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