What is a board foot of timber?

A board foot (BF) is a unit of timber volume equal to a piece that is 1 inch thick, 12 inches wide, and 12 inches long (144 cubic inches or approximately 2,360 cubic centimetres). The formula is: Board Feet = (Thickness in inches x Width in inches x Length in feet) divided by 12. Board feet measure the volume of rough or dressed timber and are commonly used to price hardwoods and large softwood orders in New Zealand and internationally. Lineal metres (LM) measure only the length, regardless of cross-section, and are used for ordering standard-sized framing, decking, and cladding.

How do I convert millimetres to inches for board feet?

To convert millimetres to inches, divide by 25.4 (since 1 inch = 25.4 mm). For example, a piece 50 mm thick is 50 / 25.4 = 1.969 inches, which is commonly called 2 inches or 50 mm dressed. To convert metres to feet, multiply by 3.28084 (since 1 metre = 3.28084 feet). This calculator accepts both metric (mm for thickness and width, metres for length) and imperial (inches for thickness and width, feet for length) inputs and converts automatically.

How many lineal metres are in a board foot?

Board feet and lineal metres measure different things, so the conversion depends on the cross-section of the timber. A lineal metre of 50 x 150 mm (approximately 2 x 6 inch) timber contains approximately 3.18 board feet (since 1 metre = 3.2808 feet, and (50/25.4) x (150/25.4) x 3.2808 / 12 = 3.18 BF). For ordering standard dressed framing timber, lineal metres are the most common unit in New Zealand. Board feet are more common when ordering hardwoods, rough-sawn timber, or importing.

Timber Board Feet and Lengths Calculator

This calculator works out how much timber you need to order, in both board feet (BF) and lineal metres (LM), for any thickness, width, length and quantity of pieces. Board feet are a volume-based unit used for pricing hardwoods and imported rough-sawn timber, while lineal metres are the standard New Zealand measure for ordering framing, decking, cladding and joinery. Choose metric (millimetres for thickness and width, metres for length) or imperial (inches and feet) inputs, or click a common NZ timber preset, such as 50 x 100 mm framing or 25 x 150 mm decking, to fill the dimensions automatically. Enter the thickness, width, length per piece and number of pieces, and the calculator converts between units (1 inch = 25.4 mm, 1 foot = 0.3048 m) and returns the total board feet, board feet per piece, total lineal metres and total volume in cubic metres, plus a breakdown of your dimensions in both units. A worked example using the default 50 x 150 mm x 3.6 m pieces shows the formula: BF equals thickness in inches times width in inches times length in feet, divided by 12. Use the results to compare hardwood or imported quotes priced in board feet against local lineal-metre pricing, and add 10 to 15 percent for waste when ordering, since figures are based on nominal rather than dressed dimensions and are indicative only.

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Standard method Board feet formula: BF = (T" x W" x L') / 12. Metric inputs converted via 1 inch = 25.4 mm, 1 foot = 0.3048 m.

1. Timber Dimensions

Input units

Thickness (mm)

Thickness (inches)

Width (mm)

Width (inches)

Length per piece (metres)

Length per piece (feet)

Number of pieces

pcs

2. Common Timber Presets

Click a preset to fill the metric dimensions above.

Results

Total Board Feet
114.42 BF
BF for all pieces

Board Feet per Piece

11.44 BF

Total Lineal Metres

36.00 LM

LM for all pieces

Total Volume

0.2700 m3

m³ of timber

Timber Details

Thickness50 mm (1.97 in)

Width150 mm (5.91 in)

Length per piece3.6 m (11.81 ft)

Number of pieces10 pieces

Board feet per piece11.44 BF

Total board feet114.42 BF

Length and Volume

Length per piece (imperial)11.81 ft

Total lineal metres36.00 LM

Total lineal feet118.11 LF

Volume per piece0.0270 m3

Total volume0.2700 m3

Worked example (matches default inputs) 50 mm x 150 mm x 3.6 m, 10 pieces:
Thickness = 50 / 25.4 = 1.969 in, Width = 150 / 25.4 = 5.906 in, Length = 3.6 / 0.3048 = 11.811 ft
BF per piece = (1.969 x 5.906 x 11.811) / 12 = 11.44 BF
Total BF = 11.44 x 10 = 114.4 BF; Total lineal metres = 3.6 x 10 = 36.0 LM

How Board Feet Are Calculated

A board foot is a unit of timber volume equal to a piece that is 1 inch thick, 12 inches wide, and 12 inches long. The standard formula is:

Board Feet = (Thickness in inches x Width in inches x Length in feet) / 12

For example, a 50 x 150 mm piece (approximately 2 x 6 inches) that is 3.6 m long (approximately 11.81 feet) contains: (1.969 x 5.906 x 11.811) / 12 = 11.45 BF. For metric inputs, this calculator converts millimetres to inches (divide by 25.4) and metres to feet (divide by 0.3048) before applying the formula.

Board Feet vs Lineal Metres

In New Zealand, timber for standard framing, decking, and cladding is usually sold by the lineal metre (LM) for a given cross-section (for example, 50 x 100 mm at $X per LM). Board feet are more commonly used when ordering hardwoods such as rimu, matai, or imported oak, or when importing rough-sawn timber from the USA or Canada where board feet are the trade standard.

Lineal metres count only the length of a piece. Board feet count both cross-sectional area and length, giving a volume-based measure. If you are quoting a hardwood job or ordering from an overseas supplier, board feet let you compare prices and quantities accurately regardless of the timber size.

Common NZ Timber Sizes and Their Board Feet Per Lineal Metre

Timber size (mm)	Common use	BF per lineal metre	BF per 3.6 m length
50 x 100 (2x4)	Framing stud	2.12	7.63
50 x 150 (2x6)	Framing, joist	3.18	11.44
50 x 200 (2x8)	Floor joist	4.24	15.25
100 x 100 (4x4)	Post	4.23	15.24
100 x 200 (4x8)	Beam, lintel	8.47	30.47
25 x 150 (1x6)	Decking	1.59	5.72
20 x 90	Weatherboard	0.76	2.74

Note: BF per LM figures are calculated from nominal dimensions. Dressed (DAR) timber is slightly smaller than nominal, but pricing is generally based on nominal dimensions.

Ordering Tips for NZ Builds

Add 10 to 15 percent to your calculated quantity for waste, cutting losses, and defects.
Standard framing lengths in NZ are 3.0 m, 3.6 m, 4.2 m, 4.8 m, 5.4 m, and 6.0 m. Choose a length that minimises offcuts for your stud height.
For decking and cladding, order in the longest practical length to reduce joins and end-grain exposure.
Hardwood suppliers (rimu, macrocarpa, totara) often quote in board feet. Softwood suppliers (pine, radiata) usually quote in lineal metres or cubic metres.
When ordering from a sawmill, specifying board feet alongside your linear and piece counts helps the miller cut efficiently.

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Sources and method: Board feet formula: BF = (T" x W" x L') / 12, per industry standard (US National Institute of Standards and Technology Handbook 67; Timber Measurement Society). Metric conversions: 1 inch = 25.4 mm exactly (ISO 31-1); 1 foot = 0.3048 m exactly. NZ common timber sizes per NZS 3603 and NZS 3604 framing standards.

This calculator provides volume and length estimates based on nominal timber dimensions. Actual dressed sizes are slightly smaller than nominal. Add an allowance for waste, cutting losses, and grade variations when ordering. Confirm dimensions and quantities with your supplier before placing orders.