Before you lift, haul or mill a log, it helps to know roughly how much it weighs. Freshly cut wood is mostly water, so a green log can weigh twice as much as the same wood once dry. This calculator estimates the volume of a log from its two end diameters and its length, then its green weight from the species.
The formula
- Volume (Smalian formula) = (area of the small end + area of the large end) ÷ 2 × length
- End area = π × (diameter ÷ 2)²
- Weight = volume × green density of the species
Smalian’s formula averages the two ends. It slightly overestimates the volume of a typical log, which is a safe error when planning a lift.
Example
A red oak log 10 ft long, 16 in across at the small end and 18 in at the large end has a volume of about 15.8 cu ft. At 63 lb per cu ft green, it weighs about 1,000 lb, half a short ton.
Green weight by species
| Species | Green weight (lb per cu ft) |
|---|---|
| Red oak | 63 |
| White oak | 62 |
| Sugar maple | 56 |
| Southern yellow pine | 52 |
| White ash | 48 |
| Douglas fir | 38 |
| Eastern white pine | 36 |
Values are typical figures from the USDA Wood Handbook. Moisture varies with the season, the part of the tree and the time since felling, so real weights can differ by 10 to 20%.
Practical uses
- Lifting and rigging: compare the weight with the rated capacity of your tractor, winch, chains or straps, with a wide safety margin.
- Hauling: add up several logs to stay under your trailer’s payload and towing limit.
- Milling: the volume helps estimate lumber yield, though sawn board feet are always lower than the log volume because of the slabs, kerf and taper.
Measuring a log
Measure diameters inside the bark if you can, or average two measurements at right angles on each end. Measure the length along the log, not in a straight line if it is crooked.
Safety
Logs roll and shift unexpectedly. Never stand on the downhill side of a log you are moving, use proper chains and hooks, and keep bystanders clear. For felling and large logs, wear a helmet, eye and ear protection, chaps and steel-toe boots.