Estimate tree log weight from end diameters and length using typical green wood for pine, oak, maple and more, or enter your own density and moisture.
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Tree Weight Formula
The Tree Log Weight Calculator estimates solid-log mass using either an end-diameter midpoint approximation or Smalian’s average-end-area method. Choose total weight, length of each log, dry-mass density, or method comparison. Diameter accepts cm, in or mm; length accepts m or ft; density accepts kg/m³ or lb/ft³; weight accepts kg, lb or metric tonnes. Pick a wood species to use its typical green density and moisture, or choose Custom and enter your own.
Here, M is dry-basis moisture as a fraction: water mass divided by oven-dry wood mass. The density ρd must be dry mass divided by the same reference volume used for the log dimensions. For green dimensions, use a green-volume/basic-density basis; oven-dry-volume density cannot be substituted without a volume-change adjustment. The calculator does not model drying shrinkage.
Variable Definitions
| Variable | Meaning | Units used by the calculator |
|---|---|---|
| W | Estimated total mass of n equal logs | kg, lb or metric tonnes |
| d1, d2 | Small-end and large-end diameters | cm, in or mm |
| L | Length of each equal log | ft or m |
| ρd | Dry mass per measured log volume | User-supplied kg/m³ or lb/ft³; reference volume must match dimensions |
| V | Volume per log; n is a positive whole number of equal logs | ft³ or m³ |
How to Calculate Tree Log Weight
- Measure the small-end and large-end diameters of the usable solid-log section. Enter each diameter with its unit.
- Measure the log length from one end to the other along the usable section.
- Pick a wood species, or choose Custom and enter dry mass per measured log volume and dry-basis moisture percentage. Enter 0% for dry wood; confirm the density volume basis.
- Choose midpoint approximation or Smalian, and enter the positive whole number of equal logs (default 1).
- Select Calculate. Expand Calculation details for volume, density, method comparison and substitutions.
These methods assume straight, solid logs with circular ends. The midpoint option infers the midpoint diameter from the ends; true Huber uses an actual midpoint measurement. Smalian uses the measured end areas. Neither method guarantees the true volume of an irregular log.
Rearranged Forms
The length and density modes explicitly solve the selected value. A is the chosen cross-sectional area factor, so V = AL; W is the known total weight of n equal logs.
Example Calculation
For one log with end diameters of 30 cm and 40 cm, length 4 m, dry mass per measured volume of 500 kg/m³ and 50% dry-basis moisture, the midpoint approximation is:
The midpoint volume is approximately 0.384845 m³, giving an estimated mass of 288.634 kg. Smalian gives approximately 294.524 kg, or 2.040816% more. These are model estimates rather than scale measurements.
Standing Tree Biomass Estimate
Choose Standing tree (biomass) to estimate a living U.S. forest tree from its species group and diameter at breast height (DBH), measured over bark at 1.37 m (4.5 ft) above ground. This is different from measuring a cut log: the aboveground estimate includes the trunk, bark, branches and foliage. It does not need a tree height or an assumed stem-form factor.
The Jenkins et al. (2003) U.S. biomass equations estimate oven-dry biomass: A = exp(b₀ + b₁ ln D), where A is aboveground mass in kg and D is DBH in cm. The coefficients depend on the selected tree group. For pine, b₀ = −2.5356 and b₁ = 2.4349. At 30 cm DBH, this gives approximately 312.9 kg of aboveground dry biomass.
Coarse roots are shown separately using R = A exp(a₀ + a₁/D): hardwood coefficients are −1.6911 and 0.8160; softwood coefficients are −1.5619 and 0.6614. A 30 cm pine has approximately 67.1 kg of coarse-root dry biomass, or 380.0 kg aboveground plus coarse roots. Roots do not include attached soil or all fine roots; the crown is already included aboveground.
Dry biomass is not freshly cut weight. If you know a representative dry-basis moisture content M, select Wet mass from supplied moisture. The calculator uses W = dry biomass × (1 + M/100), applying your percentage to each included component. For example, 50% moisture makes the estimated wet mass 1.5 times the dry biomass. A log-species moisture preset is not automatically assumed for an entire tree.
The mode accepts DBH from 2.5 cm to the selected group’s published underlying-data maximum, avoiding unsupported diameter extrapolation. These national equations are rough individual-tree estimates; species, site, crown form and condition affect real mass. Palms, tropical trees, damaged trees and lifting or hauling approval require a more suitable assessment.
What Affects Real Log Weight
- Species: Different woods have different natural densities.
- Moisture content: Green logs are often much heavier than seasoned logs.
- Bark thickness: Thick bark adds weight that may not match a simple cylinder estimate.
- Taper: Logs that narrow from one end to the other are not perfect cylinders.
- Defects: Rot, hollows, splits, and voids can reduce true weight.
Tips for Better Estimates
- Measure representative end diameters, avoiding flares and damaged sections. Either end may be entered first; Calculation details orders them by size.
- Choose a volume method explicitly. A measured midpoint is required for true Huber; averaging the end diameters is only an approximation.
- For long stems, estimate weight section by section and add the results.
- Do not use this estimate alone to approve hauling, rigging or crane capacity. Use measured loads and qualified assessment of equipment, bark, voids, moisture and uncertainty.
Common Uses
- Estimating trailer or truck payload before transport
- Planning sawmill handling and storage capacity
- Producing a rough mass estimate to discuss with a qualified lifting or transport planner
- Comparing how trimming length or reducing diameter changes total weight
