Introduction
As a forest
landowner interested in selling timber, you are naturally interested
in the price you will receive for your product and how that price
is determined. The measurement of standing timber and logs may seem
strange and complicated to you, and it is possible that you may be
quoted dramatically different prices based upon differing estimates
of the amount of timber you have and the units of measurement used.
Methods of measuring timber and the units of measurement often differ
between buyers, and, as a seller, you should have an understanding
of these methods, the units of measurement, and an idea as to a reasonable
price for your timber.
*The following information is provided by Virginia Cooperative Extension
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Measurement
of Standing Timber
The standing
timber in your woodlot has a certain value, which is commonly called
the stumpage value. Expressed in terms of dollars per unit volume
of wood, this is the amount of money you can expect to receive upon
sale of your timber. Many factors determine your stumpage value, but
the most important are the species of trees you have, the quality
and size of the trees, the location of your woodlot, the prevailing
market conditions, the terrain, and the amount of wood you have to
sell. Naturally, there are great variations in stumpage prices among
woodlots, depending upon changes in any of these factors. Thick, mature
stands of a valuable species like northern red oak, located on level
ground near a mill, will obviously bring far more money than stands
of smaller trees of lower quality species located on steep terrain
far from a mill.
Buyers of
timber will always need to conduct a survey of your woods before they
can make an offer. This survey is often called a timber cruise and
involves a series of measurements of individual trees, as well as
an assessment of factors that will influence the price of your timber.
Such factors include the terrain, the amount of road building required,
the need for culverts, the access across adjoining properties, and
the need for special best management practices (BMP's) to protect
against erosion and site deterioration after logging.
When the
timber buyer measures your trees, he will locate a series of plots
on your land and will measure each tree on each plot. Measurements
will include the diameter of the tree (Figure 1), the merchantable
height of the tree, the tree species, and often a subjective notation
of the tree quality. The tree dimensions, diameter and height, are
used to determine the volume of the tree. It is this volume, summed
over all the trees on your land, that will ultimately serve as the
basis for your stumpage price.
It is at
this point that the measurement of your timber becomes confusing.
The volume of an individual tree can be expressed in a variety of
ways, depending upon the product or the desire of the buyer. For example,
trees that are sold for pulpwood are often measured in cubic feet
or cords. A cubic foot of wood is an obvious unit of measure; however,
a cord is a stack of wood measuring 8 feet long, 4 feet high, and
4 feet wide. A solid cord, therefore, contains 128 cubic feet; however,
wood is not bought and sold in terms of solid cords. When wood is
stacked into cords, there is a considerable amount of air space between
the pieces, so that an actual cord generally contains from 80 to 90
cubic feet. Another volume term sometimes used is the cunit. A cunit
is simply 100 cubic feet of solid wood.
Even more
confusing than the pulpwood measurement of your timber is the measurement
of the larger trees that will become sawlogs. These larger trees,
usually at least 10 inches in diameter (at a point 4 1/2 feet from
the ground, referred to as breast height), are termed sawtimber trees
and contain significantly more value than pulpwood trees. Sawtimber
trees are also measured for diameter and merchantable height, where
the merchantable height is the number of 8foot logs that could be
cut out of the tree up to a minimum top diameter of 8 inches. The
diameter and height are then used to determine the volume of the tree
in boardfoot units. A board foot is a piece of wood measuring 1 inch
thick, 12 inches wide, and 12 inches long. The volume of a tree, therefore,
is measured by the number of board feet of lumber that can be sawn
out of it. This seems simple enough, but there are actually many different
ways that boards can be cut out of logs, and thus over the years many
different ways of determining boardfoot volume have evolved (Figure
2). Although dozens of different ways of expressing boardfoot volumes
exist, only three are commonly used in Virginia. These three log rules
are the Doyle Rule, the Scribner Rule, and the International 1/4Inch
Rule.
Although
these rules were developed to express the volume of logs, they are
also applied to standing trees that contain one or more merchantable
logs. The volume of a tree is simply the sum of the individual logs
that it contains.
Unfortunately,
the different log rules result in different volumes when applied to
logs (or trees) of the same dimension. In addition, these differences
are not always consistent across the normal range of log or tree sizes.
Therefore, as a seller of timber, you should be aware of these important
differences so that you can compare offers based on different log
rules.
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Measurement
of Logs
The measurement of the wood volume contained in sawlogs is commonly
known as log scaling. A log of a certain length and diameter
(always measured at the smallest end of the log) will contain a certain
number of board feet. Just how many board feet a log contains depends
upon the log rule used by the scaler. Since logs often contain defects
that reduce the merchantable wood volume, scalers will often apply
deductions to remove the estimated useless volume in a log from the
total.
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General Features
of Log Rules
Since the
first sawmill was built in the United States, over 100 log rules have
been developed, using a variety of methods. Some were based upon the
lumber tallies of individual mills, others were developed by diagramming
the crosssection of boards in the ends of logs (Figure 2), while
still others were developed using mathematical formulas. In general,
log rules must account for the taper that exists in all logs, saw
kerf (or the loss of wood as sawdust), and a fixed procedure for removing
wood on the outside of the logs for slabs. The Doyle, Scribner, and
International log rules are probably the most widely used rules in
the eastern United States.
Doyle
Log Rule
The Doyle
Log Rule, developed around 1825, is based on a mathematical formula
and is widely used throughout the southern United States. This rule
allows for a saw kerf of 5/16 inch and a slabbing allowance of 4 inches,
which is about twice the normal amount. Because of this, the Doyle
Rule is somewhat inconsistent; it underestimates small logs and overestimates
large logs. As a seller of timber, you must be aware that for smaller
logs the Doyle Rule will underestimate the actual volume of wood that
you have in your trees.
Scribner
Log Rule
The Scribner
Log Rule, developed around 1846, is a good example of a diagram rule.
It was created by drawing the crosssections of 1inch boards within
circles representing the end view of logs. A space of 1/4 inch was
left between the boards to account for saw kerf. The Scribner Rule
does not have an allowance for log taper and typically underestimates
logs, particularly if the log length is long. The Scribner Decimal
C is a different form of the Scribner Rule; it rounds the volumes
to the nearest 10 board feet. For example, 392 board feet on the Scribner
is equivalent to 390 board feet on the Scribner Decimal C scale.
International
1/4Inch Log Rule
This rule
was developed in 1906 and is based on a reasonably accurate mathematical
formula. The rule allows for a 1/4inch saw kerf and a fixed taper
allowance of 1/2 inch per 4 feet of log length. Deductions are also
allowed for shrinkage of boards and a slab thickness that varies with
the log diameter. Overall, the International 1/4Inch Log Rule is
the most consistent and is often used as a basis of comparison for
log rules.
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of Contents.
Comparison
of Log Rules
Since each
of the log rules was developed using different methods with different
assumptions, it is logical that they will not always result in the
same volumes for given size logs. Table 1 shows a comparison of the
three log rules for 16foot logs ranging in diameter from 6 to 40
inches. Compared to the International Rule, both the Scribner and
Doyle Rules underscale logs of smaller diameters. For example, a 12inchdiameter
log contains 95 board feet on the International scale, 80 board feet
on the Scribner scale, and 64 board feet on the Doyle scale. Overall,
the Doyle Rule will result in lower log volumes than the International
Rule, up to a log diameter of 30 inches. Since nearly all logs in
Virginia are below 30 inches in diameter, for all practical purposes
the Doyle Rule will underestimate the actual board footage.
Table 1.
Comparison of log rules for 16foot logs.

Log Rule
(board feet) 
Log Diameter
(inches) 
International
1/4Inch 
Scribner
Decimal C 
Doyle 
6 
20 
20 
4 
7 
30 
30 
9 
8 
40 
30 
16 
9 
50 
40 
25 
10 
65 
60 
36 
11 
80 
70 
49 
12 
95 
80 
64 
13 
115 
100 
81 
14 
135 
110 
100 
15 
160 
140 
121 
16 
180 
160 
144 
17 
205 
180 
169 
18 
230 
210 
196 
19 
260 
240 
225 
20 
290 
280 
256 
21 
320 
300 
289 
22 
355 
330 
324 
23 
390 
380 
361 
24 
425 
400 
400 
25 
460 
460 
441 
26 
500 
500 
484 
27 
540 
550 
529 
28 
585 
580 
576 
29 
630 
610 
625 
30 
675 
660 
676 
32 
770 
740 
784 
36 
980 
920 
1024 
40 
1220 
1200 
1296 
If you are
selling stumpage or logs, it is important to recognize the differences
in volume associated with the different log rules. Since stumpage
or log prices are based on the timber or log volume, you will receive
substantially more income with the rules that scale your sizes higher.
For example, take a log of 16 inches diameter x 16 feet in length
and a value of $100 per thousand board feet. This log would have the
following volumes and values based upon the different log rules:
Log
Diameter
(in.) 
Log Rule 
Volume
(board feet) 
Value ($) 
16 
International 
180 
18.00 
16 
Scribner Decimal
C 
160 
16.00 
16 
Doyle 
144 
14.40 
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Log Rule
Controversy
It is fair
to say that not everyone agrees on the appropriate log rule to use.
Sellers of logs and timber prefer the rules that give them the greatest
return, while purchasers obviously prefer log rules that underscale
the actual volume in trees or logs. It is important for you, as a
seller of timber, to realize that buyers are in a risky situation.
Trees and logs often have hidden defects that may greatly reduce their
merchantable volume and value. With hardwood timber and logs, the
quality often is a more important determinant of value than the mere
volume. A purchaser of logs must be adept at recognizing the tree
quality of the raw material and adjust the price accordingly. Some
logs may have a high enough quality to enable their use for veneer.
Such logs generally command a premium price, and the differences between
volumes determined by the different log rules become especially important.
Buyers of
timber and logs often prefer the Doyle Rule, since we have seen that
this rule underestimates the board footage (compared to the International
1/4Inch Rule) for logs less than 30 inches in diameter. However,
sawmillers justifiably argue that the milling costs for smalldiameter
logs are much higher, and thus they should have a reduced value. The
Doyle Rule compensates the sawmiller by underscaling the smaller logs.
The important
thing for you to remember is that different log rules exist, and the
buying or selling of stumpage or logs should be based upon open agreement
as to the log rule to be used. Any of the three rules discussed here
can serve as a useful method for scaling logs, as long as both the
buyer and seller recognize and agree to its use. Prices can easily
be adjusted to reflect the log rule being used.
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Conclusion
When selling
standing timber or logs, you should expect to receive the fair market
price for your product, no more and no less. Bargains often come at
considerable expense, including poor logging jobs, site degradation,
or perhaps default on the part of the purchaser. You will have the
best chance of receiving the fair market price if you use a sealed,
competitive bid process and receive as many bids as possible from
reliable purchasers. Your Virginia Department of Forestry county forester,
consulting foresters, and industrial landowner assistance foresters
can provide you with assistance in this important process.
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Approximate Timber Conversion Factors
1 cord = 500 board feet
1 cord = 79 cubic feet of solid wood
1 acre = 43,560 square feet
