Log Weight Calculator
About Log Weight Calculation
The log weight calculator calculates the volume and mass of logs, boards and timber beams from their dimensions, wood species, density and number of pieces. It helps estimate wood weight for transport, storage and deliveries of timber. If the wood volume is already known, its mass can be calculated directly from density.
Guidelines and recommendations
Calculating wood volume
Boards and beams. The volume of one piece is the product of its length, width and thickness. Length is entered in metres, while width and thickness are in millimetres. To obtain a volume in m3, the cross-sectional dimensions are divided by 1000 to convert them into metres.
V1 = (b / 1000) × (h / 1000) × L
Here V1 is the volume of one piece in m3, b is the width in mm, h is the thickness in mm and L is the length in m. A rectangular cross-section with constant dimensions along the full length is assumed.
Log with a mid-length diameter. When the diameter at the middle of the log is known, the volume is calculated using the cylinder formula. The diameter is converted from centimetres to metres.
V1 = π × deff2 × L / 4
Here deff is the calculated diameter in metres, L is the log length in metres and π ≈ 3.14159. This method assumes that the cross-sectional area remains constant along the log.
Log with two end diameters. If the diameters at the ends differ, the log is modelled as a circular frustum (truncated cone). The formula accounts for a gradual linear change of diameter between the ends.
V1 = π × L × (d12 + d1 × d2 + d22) / 12
Here d1 and d2 are the calculated end diameters in metres. This method accounts for log taper and differs from treating the log as a cylinder with the arithmetic mean of the two diameters.
Bark adjustment. If the diameters are measured over bark, bark thickness can be deducted before determining the volume of wood without bark. Thickness is deducted from both sides of each diameter.
deff = (d - 2 × t) / 100
Here d is the measured diameter in cm and t is bark thickness on one side in cm. For example, a 30 cm diameter and 1 cm bark thickness give a calculated diameter of 28 cm. With two end diameters, the adjustment is applied to each end. Without bark deduction, the original measured diameters are used.
Density and mass calculation
Wood density. A reference value in kg/m3 is used for the selected species. For example, the values are 510 kg/m3 for pine, 450 kg/m3 for spruce and 700 kg/m3 for oak. These are approximate average values for air-dried wood at about 12% moisture content, not fixed properties of every specimen.
Effect of moisture. As moisture content increases, the mass of wood generally increases. For freshly felled or wetter wood, use a density appropriate to its actual condition. No automatic moisture correction factor is applied because the density change depends on species, initial condition and moisture content.
Mass of one piece. The calculated geometric volume is multiplied by the selected wood density.
m1 = V1 × ρ
Here m1 is the mass of one piece in kg, V1 its volume in m3 and ρ the density in kg/m3. If the total volume is known, the same formula is applied directly to that volume.
Total volume and mass. For identical pieces, the volume and mass of one piece are multiplied by the quantity N.
Vtotal = V1 × N
mtotal = m1 × N
N must be a positive whole number. All pieces in the batch are assumed to have identical dimensions and density. Intermediate calculations are not rounded. Only displayed results are rounded.
Mass per linear metre. For boards and beams, the mass of a 1 m length is also calculated. It depends only on the cross-sectional dimensions and material density.
mm = (b × h × ρ) / 1000000
Here mm is mass per linear metre in kg/m, b and h are the cross-sectional dimensions in mm and ρ is density in kg/m3. For example, a 100 × 150 mm pine beam with a density of 510 kg/m3 has a calculated mass of 7.65 kg/m.
European standards and accuracy of input data
European standards EN 338, “Structural timber - Strength classes”, and EN 384, “Structural timber - Determination of characteristic values of mechanical properties and density”, are used to assess properties of structural timber. EN 338 specifies mean and characteristic density values for strength classes. The calculator uses approximate species-based densities, which must not be confused with the characteristic density of a particular strength class.
European standard EN 13183-1, “Moisture content of a piece of sawn timber - Part 1: Determination by oven dry method”, describes how moisture content is determined from the difference between the mass before and after oven drying. Moisture content is expressed as a percentage of the oven-dry wood mass. This matters when using reference densities and comparing the mass of dry and wet timber.
Result accuracy. The calculation uses the specified density and an idealised geometry for each piece. Actual mass is affected by wood variability, moisture, dimensional tolerances and log shape. For a better estimate, use measured dimensions and a density that reflects the actual condition of the material.
FAQs
How much does one cubic metre of pine, spruce or oak weigh?
At the reference densities used here, 1 m3 of pine weighs about 510 kg, spruce 450 kg and oak 700 kg. These are approximate figures for wood at about 12% moisture content. Actual weight per cubic metre can differ considerably depending on moisture and the density of the individual piece.
Why can equal volumes of wood have different weights?
Wood weight depends not only on volume but also on density, which varies among species and individual pieces. Moist wood also contains the additional mass of water. Thus, freshly felled and dried wood can have substantially different masses even at the same volume.
How important is the difference between the diameters at the ends of a log?
The more a log tapers from one end to the other, the greater the difference between calculating with the mean diameter and using the frustum formula. For example, a 4 m log with end diameters of 20 and 40 cm has a volume of about 0.2932 m3 according to the frustum formula, versus about 0.2827 m3 using the mean diameter of 30 cm. The difference is approximately 3.7%.
How should bark be accounted for when calculating log mass?
If the required result is the mass of wood without bark, subtract bark thickness from both sides of each measured diameter. For example, a bark thickness of 1.5 cm reduces a measured diameter by 3 cm. If diameters were already measured without bark, no additional adjustment is needed.
How is the total weight of a batch of boards or beams calculated?
First, the volume of one piece is calculated from its length, width and thickness, then multiplied by wood density. The resulting mass is multiplied by the number of identical pieces. For example, five pine boards measuring 50 × 200 mm and 4 m long, at a density of 510 kg/m3, have a total volume of 0.2 m3 and a calculated mass of 102 kg.