Calculating the m³ of wood allows you to know precisely the volume of one or more pieces before an order, a job site, or a quote. The calculation is particularly common for professionals in carpentry, timber construction, joinery, timber trading, or sawmilling.
Do you need to calculate the volume of several beams, rafters, purlins, or other pieces of wood? Use our calculator below to get the total volume directly.
Calculating wood volume in m³ at a glance
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To calculate wood volume in m³, the formula is volume in m³ = length × width × thickness, with all dimensions in meters.
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For cross-sections in millimeters, keep millimeters and divide by 1,000,000: width in mm × height in mm × length in m × quantity ÷ 1,000,000.
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The wood species has no impact on the volume. One m³ of oak and one m³ of Douglas fir take up the same space. Species affects weight and price, not volume.
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The volume to order is higher than the calculated volume. The difference depends on the lengths available from your supplier and on how you organize your cutting list. For the same list of parts, it can vary from single to double.
Wood volume calculator in m³
Enter the dimensions and quantity of your pieces to automatically calculate their total volume in m³.
Our calculator is suitable for beams, rafters, purlins, joists, posts, planks, studs, battens, and boards—in other words, any piece with a rectangular or square cross-section.
You can add several types of pieces with different cross-sections, lengths, and quantities. The volume of each item is calculated automatically, then added up to obtain the total volume.
How to calculate 1 m³ of wood?
To calculate volume—that is, the volume of a piece with a rectangular cross-section (m³)—you need three dimensions and a quantity. The formula is: volume in m³ = length in m × width in m × thickness in m.
For several identical pieces, simply multiply the unit volume by the number of pieces.
Example :For a beam 5 m long, 20 cm wide and 10 cm thick, after converting to meters: 5 × 0.20 × 0.10 = 0.10 m³. For 12 identical beams: 0.10 × 12 = 1.20 m³.
How to calculate wood volume in m³ with dimensions in millimeters?
Structural timber cross-sections are often given in millimeters and lengths in meters. You can calculate their volume directly without converting each dimension to meters using the following formula : volume in m³ = width in mm × height in mm × length in m × quantity ÷ 1,000,000.
Dividing by 1,000,000 converts the cross-section expressed in mm² directly into m², without having to convert width and height to meters separately. You can therefore keep the cross-section dimensions in millimeters and apply the formula above directly.
Example :For 20 rafters of 63 × 75 mm and 4 m long: 63 × 75 × 4 × 20 ÷ 1,000,000 = 0.378 m³. The batch therefore represents 0.378 m³ of wood.
Example : calculating m³ of structural timber
In a framing project, it is common to use pieces of wood with different cross-sections and lengths. Each item must then be calculated separately, and the different volumes are added together to obtain the total volume of wood required.
On a small frame, the calculation can for example look like this:
|
Element |
Cross-section |
Length |
Quantity |
Volume |
|
Rafters |
63 × 75 mm |
4 m |
20 |
0.378 m³ |
|
Purlins |
100 × 225 mm |
6 m |
5 |
0.675 m³ |
|
Posts |
150 × 150 mm |
3 m |
4 |
0.270 m³ |
|
Total |
1.323 m³ |
Whether you start from a plan, a bill of materials, or a cutting schedule, calculate the volume of each item separately, then add the results to obtain the total volume.
For projects with a large number of pieces, volume calculation can also be automated using CAD, quantity takeoff, or site management software. The WoodPartners calculator, for its part, lets you quickly verify a volume or calculate a limited list of items without using specialized software.
Good to know
Volume calculation does not determine whether the cross-section of a beam, purlin, or other piece is suitable for your structure. Sizing according to span and supported loads is a structural calculation, to be carried out by an engineering office before pricing.
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How to calculate the volume of wood that is not rectangular?
To calculate the volume of non-rectangular wood, the method depends on its shape. For a log, you can use a volume formula adapted to roundwood, such as Huber's formula. For an irregular piece, divide it into several simple volumes, calculate them separately, then add the results.
Case of a log or roundwood
A log, i.e., a felled and delimbed trunk before its sawmill breakdown, is not measured like a squared piece with a square or rectangular cross-section.
Several methods make it possible to estimate the volume of a log. In France, Huber's formula is commonly used for commercial volume measurement. It consists of treating the log as a cylinder based on its diameter measured at mid-length. Its accuracy depends in particular on the regularity of the diameter along the length.
Huber's formula is calculated as follows: V = (π × D² × L) ÷ 4
With:
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V : volume in m³ ;
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D : median diameter in meters ;
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L : length in meters.
Example :For a log 4 m long and 40 cm in median diameter: (3.1416 × 0.40² × 4) ÷ 4 ≈ 0.503 m³
Other methods exist, such as Smalian's formula, based on the cross-sections at the two ends of the log, or Newton's, which also takes into account the cross-section at mid-length.
Case of an irregular piece of wood
If a piece has an irregular shape or dimensions that vary along its length, divide it as much as possible into several simple volumes. Calculate each part separately, then add the results.
Example : a 3 m piece measures 10 × 10 cm over its first 2 meters, then 10 × 8 cm over the last meter. Its volume is 0.020 m³ + 0.008 m³, i.e., 0.028 m³ in total.
Are you preparing a tender or a quote? WoodPartners lists manufacturers, sawmills, and distributors of structural timber and sawn timber, with their ranges and available sizes.
Should you allow for extra waste beyond the calculated volume?
Yes, you generally need to allow for a margin compared with the theoretical volume. The volume actually required depends in particular on the lengths available from the supplier, the cuts to be made, the offcuts generated, possible defects in the wood, and the ability to reuse certain offcuts. There is therefore no universal percentage.
For example, if you need 2.80 m pieces, but your supplier only offers 4 m lengths, cutting will generate offcuts. Some can sometimes be reused for other pieces, provided you organize the cutting plan accordingly.
The volume actually required may depend in particular on:
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the lengths available from the supplier ;
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the dimensions of the pieces to be cut ;
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the offcuts generated ;
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possible defects in the wood ;
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the possibility of reusing an offcut for another piece.
There is therefore no universal waste percentage to apply to all orders.
The volume calculation gives the theoretical volume required. To prepare an order, you then need to take into account the lengths available from your supplier and organize the cuts to limit wood offcuts.
Yves Samama, WoodPartners