Pine Timber Volume-to-Weight Conversions

Measurement standards for pine timber are changing. Most high-production pine sawmills have converted to weight scaling and purchase timber by the ton (2,000 pounds). Mills producing chips, pulp, or paper are almost exclusively measuring timber by weight. However, many high-grade pine lumber and specialty mills still measure volume using the Doyle Log Rule and pay per MBF (1000 board feet). A local woodyard may still stick-scale pulpwood and pay by the cord (128 cubic feet). The diversity of measurements within the forest industry is confusing to timber buyers as well as timberland owners. The volume-to-ton conversions presented are "ballpark" figures close enough for most timberland owners' needs. The conversions presented will be useful for loblolly, shortleaf, longleaf, and slash pines only. Do not use these conversions for spruce pine or for damaged and dead timber. You should use the conversions only as estimates and guidelines. Wood characteristics, like moisture content and specific gravity, vary from tree to tree, making the exact volume-to-ton conversion for your timber different.

Volume-to-ton Conversions

For weight conversion you can divide pine timber into three product types:

• shortwood pulpwood (8 feet and less in length),
• longwood pulpwood (more than 8 feet) and
• chip-n-saw or pine sawtimber.

Shortwood

Standard weight of 2.6 tons (5,200 pounds) per cord for shortwood pine pulpwood.

Longwood

Longwood pulpwood is a common product delivered tree-length. Pines with diameters (at breast height) ranging from 4 up to 22 inches can qualify for pulpwood.

Species of Longwood Pulpwood	Weight per Cord
Loblolly or Shortleaf	2.6 Tons (5,200 lbs) per Cord
Longleaf or Slash	2.775 Tons (5,550 Lbs) per Cord

Sawtimber

The Doyle Log Rule commonly is used to estimate the volume of lumber in standing trees. The Doyle Rule underestimates volume in small diameter trees (10 to 16 inches) and overestimates volume in very large trees (30+ inches). There also tends to be a higher percentage of waste when lumber is produced from small diameter trees. To compensate for waste and the Doyle log rule's inaccuracies, volume-to-ton conversions are presented by 2-inch diameter classes. Determining the average tree size is critical in getting an accurate conversion from volume-to-tons (Figure 1). Weight can vary from a high of 12.70 tons/MBF for 10-inch diameter timber down to 4.81 tons/MBF for 30-inch timber. Diameter used here is the average diameter at breast height (dbh) for the timber stand.

Figure 1. The influence stem diameter(dbh) is on weight of 1000 board feet of sawtimber. The relationship equation (R²= .994) is: TONS/MBF = 22.983-1.2395(dbh)+ .0211(dbh²)

You can use the chart above to find the volume to weight conversion or try the "Timber Conversion" calculator in the Tools section.

Use of Conversions

Converting pine timber volume to tons can be useful for tax recordkeeping, growth monitoring, and marketing. You usually take inventories of standing timber first in units of volume (cords and MBF). Volume tables, not weight tables, are readily available for standing timber. If you need the weight of pine timber, you can change the inventory to tons. Multiply volume by the appropriate tons/volume conversion as shown in Example 1.

To help monitor a logging operation, you can change the value of 1298 tons to truckloads of products. Divide the weight by 25 tons (average payload for a loaded truck weighing 80,000 pounds total) to estimate the number of truckloads of pine timber to be harvested.

Example: 1298 tons / 25 tons = 52 truckloads of products. Conversion by product would result in 34 truckloads of sawtimber, 5 truckloads of chip-n-saw, and 12.5 (about 13) truckloads of pulpwood.

You can also use conversions to change a bid to familiar units. Most timberland owners are more comfortable knowing the $/cord or $/MBF bid price. You can estimate these from a $/ton bid by multiplying the bid by tons/volume, as in Example 2. Look closely at the effect tree diameter has on the equivalent price per MBF, Doyle Log Rule. Selling sawtimber by the ton is tricky. The moral here is large diameter timber should receive more per ton than small diameter timber.

You can also estimate a $/ton bid price by dividing the $/cord or $/MBF bid by the tons/volume conversion, as in Example 3.

When selling timber on a pay-as-cut basis, you can use conversions to compare two different bids, one based on volume and the other tons. Example 4 shows this. Before deciding which bid to take, find out if the product standards at competing mills are comparable. Some mills may pay a lower $/ton price but harvest more tons per acre, resulting in more dollars to the timber owner.

Summary

As a timber owner, you can benefit from knowing how to convert from volume to tons. Conversions let you maintain timber inventories using familiar units. They also help you compare timber bids that differ in units of measure. Tree size affects the amount of waste from lumber production as well as the accuracy of the Doyle Log Rule that estimates sawtimber volume. Therefore, sawtimber volume-to-ton conversion is most accurate when you know the average tree diameter.