Calculate board feet (BF) and lineal metres for any timber size and quantity. Enter the thickness, width, length, and number of pieces. Supports both metric (mm and metres) and imperial (inches and feet) inputs.
Use this calculator to work out how much timber to order for framing, decking, cladding, joinery, or hardwood projects.
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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
mm
in
mm
in
m
ft
pcs
2. Common Timber Presets
Click a preset to fill the metric dimensions above.
Results
Total Board Feet
-
BF for all pieces
Board Feet per Piece
-
BF
Total Lineal Metres
-
LM for all pieces
Total Volume
-
m³ of timber
Timber Details
Thickness-
Width-
Length per piece-
Number of pieces-
Board feet per piece-
Total board feet-
Length and Volume
Length per piece (imperial)-
Total lineal metres-
Total lineal feet-
Volume per piece-
Total volume-
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.
Area Calculator: floor, wall, and surface area for any shape.
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.
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