Log Weight Calculator

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Walk-through

How to Use This Calculator

3 steps

1

Enter the diameter and length

Measure the log's diameter in inches — for a tapered log, use the average or mid-point diameter, since the calculator assumes a uniform cylinder. Enter the length in feet.

2

Pick a species

Choose the wood species from the dropdown: Oak, Pine, Maple, Douglas Fir, Birch, or Poplar. Density varies significantly by species, so this choice has a large effect on the result.

3

Pick a moisture state and read the weight

Choose Green (freshly cut), Air-dried, or Kiln-dried to match the log's actual condition. The result updates instantly, showing total weight in pounds and kilograms.

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Reference

Formula & Methodology

1 formula

Log weight formula

weight = (pi / 4) x diameter^2 x length x density(species, moisture)

The log is modeled as a cylinder. Volume equals (pi/4) times diameter squared times length. That volume — converted to cubic feet — is multiplied by the species' density at the selected moisture state (in pounds per cubic foot) to get total weight. Density figures are standard wood-density reference values sourced from USDA Forest Products Laboratory species tables.

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Glossary

Key Terms Explained

7 terms

Green wood Wood from a tree that has just been cut, still holding most of its natural moisture content — sometimes 50% or more of its total weight is water. Green wood is the heaviest state a log will ever be.

Dry density The mass per unit volume of wood after most of its moisture has evaporated, measured in pounds per cubic foot (lb/ft³). Dry density is what's typically listed for lumber and structural design because it doesn't fluctuate with weather.

Species The type of tree the log came from. Species determines the wood's cellular density, which is the single biggest factor in how much a log of a given size weighs — dense hardwoods like oak weigh far more than softwoods like pine.

Cylinder volume The formula (pi/4) x diameter^2 x length, used to approximate a log's volume by treating it as a uniform cylinder. Real logs taper, so this is an approximation based on the average diameter.

Moisture content The percentage of a log's weight that is water. Green wood can be 50-100%+ moisture content by dry weight; air-dried seasoned wood is typically 15-20%; kiln-dried lumber is brought down to 6-8%.

Board foot A unit of lumber volume equal to a piece 1 foot long, 1 foot wide, and 1 inch thick (144 cubic inches). Used for pricing sawn lumber rather than weighing a round log.

Log scale A system (such as the Doyle or Scribner log rule) used by loggers and sawmills to estimate the usable lumber volume in a round log, accounting for the waste from squaring off a cylinder. This calculator estimates raw weight, not sawn lumber yield.

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Scenarios

Real-World Examples

3 worked examples

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Firewood processor

12in diameter, 8ft, oak, green

Diameter 12 in Length 8 ft Species Oak Moisture Green

A freshly cut 12-inch, 8-foot oak log weighs about 390 lb. That's heavy enough that a trailer load of similar logs adds up fast — worth checking axle ratings before hauling multiple green oak logs at once.

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Sawmill operator

12in diameter, 8ft, pine, air-dried

Diameter 12 in Length 8 ft Species Pine Moisture Air-dried

The same size log in air-dried Southern yellow pine weighs about 239 lb — noticeably lighter than the green oak example, both because pine is a lighter species and because air-drying has already removed a lot of the moisture weight.

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Comparing moisture states

12in diameter, 8ft oak — green vs. kiln-dried

Green ~390 lb Kiln-dried ~277 lb

The identical oak log loses roughly 29% of its weight going from green to kiln-dried, entirely from moisture loss — the wood fiber itself doesn't change, only the water content.

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Deep Dive

Understanding Log Weight

3 chapters · 3 min read

Estimating a log's weight matters for firewood haulers planning trailer loads, sawmill operators quoting jobs, and DIYers wondering if they can lift or move a felled tree section safely. This calculator uses a simple cylinder-volume formula combined with reference wood densities to give a quick, reasonably accurate estimate.

How the calculator works

The calculator treats a log as a uniform cylinder: volume = (pi/4) x diameter² x length. That volume is then multiplied by the selected species' density at the chosen moisture state to get total weight. Density values come from USDA Forest Products Laboratory reference tables, expressed in pounds per cubic foot.

Moisture state has a large effect: a green (freshly cut) log can weigh 30-80% more than the same log after it has fully air-dried, because green wood is still carrying much of its natural water content.

Inputs and what they mean

Diameter should be the log's average diameter in inches — most logs taper from the butt end to the tip, so using the mid-point diameter gives a more accurate estimate than measuring only the thick end.

Length is the log's length in feet. Species has the single largest effect on weight after size — dense hardwoods like oak and maple weigh substantially more than softwoods like pine or Douglas fir at the same dimensions. Moisture state (green, air-dried, or kiln-dried) should match the log's actual condition; guessing wrong here is the most common source of estimate error.

Limits and edge cases

This calculator does not model taper — it assumes a perfect cylinder, so very tapered or irregularly shaped logs will be somewhat overestimated if you measure the butt-end diameter instead of the average. It also doesn't account for knots, rot, or bark, which can add or subtract a few percent from the true weight. For precise commercial weighing (timber sales, shipping manifests), use an actual scale rather than an estimate.

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Questions

Frequently Asked Questions

6 questions

Why is green wood so much heavier than dry wood?+

A freshly cut (green) log is still holding most of its natural moisture content, sometimes 50% or more of its total weight. As the log seasons and loses moisture, the weight drops — dense species like oak can lose roughly a quarter of their weight going from green to air-dried.

Does the species of wood really matter that much?+

Yes. Density varies widely by species — a green oak log can weigh nearly a third more than a green pine log of the identical size, because oak's cell structure is simply denser than pine's.

What formula does this calculator use?+

It treats the log as a cylinder: volume = (pi/4) x diameter^2 x length. That volume is then multiplied by the species' density at the selected moisture state (green, air-dried, or kiln-dried) to get total weight.

How is this useful for firewood?+

Firewood haulers and processors use log weight to estimate truck or trailer loads, since weight limits matter more than volume for towing and axle ratings. Green logs are noticeably heavier to haul than seasoned ones.

Does the calculator account for taper?+

No — it assumes a uniform cylinder. Most logs taper from butt to tip, so use the average diameter along the log's length (or the mid-point diameter) for the most accurate estimate.

What units does the result use?+

The main result is in pounds, with the kilogram equivalent shown alongside it. Diameter is entered in inches and length in feet.

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