How much does a log weigh?

It depends on diameter, length, species, and moisture state. A typical mid-size Douglas fir log (30-36 cm diameter, 5 m long) weighs around 288 kg green, using Huber's formula (volume from the mid-diameter) times the species' green density. Denser hardwoods like oak weigh much more for the same size, and drier logs weigh less.

Why is a freshly cut log so much heavier than firewood?

Freshly felled ("green") wood can be over half water by weight. As it air-dries or is kiln-dried, that moisture leaves and the weight drops substantially -- this calculator's moisture-state option models that drop instead of only giving you the green (heaviest) figure.

Is log weight priced by the tonne in Australia?

Yes -- Australian timber and firewood suppliers commonly quote green roundwood by the tonne. Divide this calculator's kilogram output by 1,000 and multiply by your supplier's per-tonne rate to cross-check a quote.

Log Weight Calculator | Tapered Round Log Weight (kg)

Log Weight Calculator: How Much Does a Round Log Weigh?

A round log's weight depends on its diameter, length, and wood species -- get it wrong and a trailer, chainsaw mill, or front-end loader can be overloaded, or a firewood delivery short-changed. This calculator applies the standard forestry formula for a tapered log (Huber's mid-diameter approximation) to your log's small-end and large-end diameter and length, then multiplies by a species-specific green-wood density to give you the weight per log, the total for a full load, and an estimated cost.

How to Use the Log Weight Calculator

Enter the diameter at the log's smaller (top) end and its larger (butt) end, with units.
Enter the log's length and the quantity of logs you're weighing.
Pick a wood species preset (each sets a green-density figure), or enter a custom density.
Choose the moisture state -- green (freshly felled), air-dried, or kiln-dried -- since a dried log weighs much less.
Choose your output mass unit and read off the per-log weight, total weight, and estimated cost.

The Math Behind the Calculation

A felled log tapers from a wider butt end to a narrower top, so the calculator uses Huber's formula, the standard forestry mid-diameter approximation: mid-diameter dm = (small-end diameter + large-end diameter) / 2, then volume V = length x (pi x dm^2) / 4 -- the same as treating the log as a cylinder at its average diameter. Weight = volume x density x quantity, where density is the species' green (freshly felled) figure, scaled down if you select air-dried or kiln-dried.

Worked example: a Douglas fir log with a 30 cm small-end diameter, 36 cm large-end diameter, 5 m long, green. Mid-diameter = (0.30 + 0.36) / 2 = 0.33 m. Volume = 5 x (pi x 0.33^2) / 4 ~ 0.428 m^3. At Douglas fir's green density of 673 kg/m^3, weight ~ 0.428 x 673 ~ 288 kg per log.

Pro Tips

At a typical Australian price of around AU$0.18 per kg for green roundwood, the 288 kg Douglas fir log from the worked example above would cost roughly AU$52 in raw material -- felling and haulage are additional.

Green wood is much heavier than seasoned wood -- a kiln-dried log in this calculator weighs only around 60% of the green figure, so don't use a green density to estimate a stack of dried firewood.
Species matters more than most people expect: green density ranges from around 449 kg/m^3 for western red cedar to over 1,200 kg/m^3 for live oak -- nearly a 3x spread -- so match the species preset to what you're actually hauling.