How Much Does a Log Weigh? Red Gum, Ironbark, Box and Spotted Gum
A freshly cut red gum log 30cm (12in) across and 1m (3.3ft) long weighs roughly 80kg, and a seasoned log of the same size can be closer to 60kg. That gap is why a single "log weight" number is never quite right. Weight comes down to three things: how big the log is, which species it is, and how much water is still in it. This guide gives you the numbers for red gum, ironbark, box and spotted gum, plus a calculator so you can estimate your own logs.
The quick formula for log weight
A log is close to a cylinder, so you can work out its volume and multiply by the timber’s density:
Weight (kg) = 3.14 × (diameter ÷ 2)² × length × density
Use metres for diameter and length, and kilograms per cubic metre (kg/m³) for density. For example, a 0.3m diameter, 1m long log has a volume of about 0.071m³. At 1,165kg/m³ that is about 82kg.
Typical density of red gum, ironbark and box
Australian hardwoods are heavy, and many sink in water when green. The figures below come from published timber property data. Seasoned (air-dry) density is measured at about 12% moisture content. Green or unseasoned density is for freshly cut timber, and it varies with season, tree and site.
| Species | Green (freshly cut), kg/m³ | Seasoned (about 12% moisture), kg/m³ |
|---|---|---|
| River red gum | about 1,130 to 1,200 | about 710 to 910 |
| Grey ironbark | about 1,170 to 1,250 | about 1,105 |
| Red ironbark | about 1,160 | about 1,050 to 1,120 |
| Grey box | about 1,230 | about 1,105 to 1,120 |
| Coast grey box | about 1,200 | about 1,100 |
| Spotted gum | about 1,180 | about 990 to 1,010 |
| Yellow box | no reliable figure found | about 1,070 to 1,100 (moisture content not stated by sources) |
These are typical values for sawn or standard-reference timber, not measurements of your logs. Real logs vary from tree to tree.
Worked examples: 1m (3.3ft) logs
These use the middle of each range, a straight 1m length and a perfect cylinder.
| Diameter | Volume | River red gum, green | River red gum, seasoned | Grey ironbark, green | Grey box, seasoned |
|---|---|---|---|---|---|
| 15cm (6in) | 0.018m³ | 21kg | 14kg | 21kg | 20kg |
| 20cm (8in) | 0.031m³ | 37kg | 25kg | 38kg | 35kg |
| 30cm (12in) | 0.071m³ | 82kg | 57kg | 86kg | 79kg |
| 40cm (16in) | 0.126m³ | 146kg | 102kg | 152kg | 140kg |
Weight climbs with the square of the diameter, so doubling the diameter quadruples the weight. A 40cm (16in) log is almost 80% heavier than a 30cm (12in) one, even though it looks only a third wider. For a log twice as long, simply double the figure.
Log weight calculator
Pick a species, choose green or seasoned, and enter the average diameter and length. The result is a range based on the density figures above.
Why real logs weigh more or less than the estimate
Moisture. Water is the biggest swing factor. Using the middle of the ranges above, seasoned river red gum can be roughly 30% lighter than the same log freshly cut. Ironbark and box lose less, roughly 10% in these tables, because their seasoned density is already very high.
Taper and shape. The calculator treats a log as a straight cylinder. Most logs are fatter at the butt end, so measure the diameter around the middle, or average the two ends.
Bark, knots and hollows. Bark adds a little weight, while hollows and rot take it away. A log with a hollow centre can be much lighter than the estimate.
Species mix-ups. "Red gum", "ironbark" and "box" each cover several species, and local names overlap. If you are unsure what you have, treat the estimate as a rough guide only.
Using the weight to plan a lift
Once you have a number, compare it with the rated capacity of whatever you plan to use to move or lift the log. Add a generous margin, because a log that is dragged, swung or jerked puts more load on equipment than the same log hanging still. Any chain, hook, crane, loader or forklift you use should be rated for the load. This guide is for estimating weight only, and it is not a lifting plan.
A 30cm (12 in) green log of these species is already 80kg or more per metre, which is a team job or a job for the right tools. If you move logs this size regularly, our log handling tools range covers cant hooks, timberjacks and tongs.
Sources
- Wood Solutions (woodsolutions.com.au): density per standard (seasoned and unseasoned) for river red gum, spotted gum, grey ironbark, red ironbark, grey box and coast grey box.
- Queensland Government timber properties pages and Timber Queensland data: seasoned density for spotted gum, ironbark and box species.
- Published timber density tables for the river red gum range, plus merchant species data sheets and general references for yellow box and the upper grey ironbark figure.
Figures are approximate and for estimating only. Weigh a sample log if you need an accurate number.