How Much Lumber in that Tree? (E2915)
Measuring diameter and height to determine tree volume.
There are times when a woodland owner may want to determine the board foot volume of certain trees in his or her woodlot for building purposes or for sale. Measuring the volumes of standing trees enables the property owner to select the proper combination of available trees to provide the desired amount of lumber. Volume calculations can also help the woodland owner avoid harvesting more trees than necessary and can give him or her an accurate accounting of the number of board feet for sale.
Large trees that will yield boards for lumber are called sawtimber trees. Sawtimber is measured and sold in terms of board feet. A board foot is 1 inch thick, 1 foot wide and 1 foot long. The first step in determining the board foot contents of standing trees is measuring their diameters and usable heights. Tables 2, 3 and 4 summarize these volumes using various log rule techniques.
Anyone can determine the board foot content of their trees by following a few simple steps. This bulletin describes how to estimate the amount of lumber in a tree with easytomake tools. If an estimate of the entire woodlot is needed, however, the owner should contact an area forester or a consulting forester for this service. More complex techniques are involved in estimating volumes on a large scale, which are beyond the scope of untrained individuals.
Measuring Diameter
Tree diameters are measured at breast height, which is 41 ⁄2 feet above the average ground level. Although diameter tapes are often used to take this measurement, another tool, called a Biltmore stick^{1}, is easy to construct in the home workshop. Use a straight piece of hardwood that is free from knots or other defects, as shown in Fig.1. The stick should be 30 inches long, 1 ⁄2 inch thick and 11 ⁄2 inches wide, and beveled on one edge.
Sand the sides and edges of the stick smooth. The stick is then graduated on the unbeveled side according to the figures given in Table 1.
^{1}The Biltmore stick may also be purchased from forestry equipment catalogues such as Forestry Suppliers or Ben Meadows.
Diametergraduations on a stick 
Distance in inches from end of stick to diameter graduations 
Diametergraduations on stick 
Distance in inches from end of stick to diameter graduations 
5 
4.6 
18 
13.7 
6 
5.4 
19 
14.3 
7 
6.2 
20 
14.9 
8 
7.0 
21 
15.5 
9 
7.7 
22 
16.0 
10 
8. 
23 
16.6 
11 
9.2 
24 
17.1 
12 
9.8 
25 
17.7 
13 
10.5 
26 
18.2 
14 
11.2 
27 
18.7 
15 
11.8 
28 
19.2 
16 
12.5 
29 
19.7 
17 
13.1 
30 
20.2 
Measure tree diameters with the Biltmore stick in the following way (see Fig. 2):
1. Hold the stick 25 inches from your eyes in a horizontal position. Hold the beveled edge of the stick against the trunk of the tree at breast height.
2. Look straight at the tree without moving your head from side to side. Adjust the stick so that the left or zero end is lined up with the left side of the tree.
3. Without moving your head, shift the line of sight to the righthand side of the trunk.
4. Read the diameter on the stick nearest the point at which the line of sight crosses it.
Tree diameter can also be measured using an ordinary tape measure. Wrap the tape around the circumference of the tree at 4.5 feet above its base. Divide the circumference by 3.14 (π) to calculate the diameter of the tree.
Measuring Height
Tree heights are measured in units of 16foot logs or fractions thereof. In slender, straight trees, this measurement is taken to a point on the upper trunk of the tree where the diameter inside the bark is 8 inches. With older trees, however, excessive branching or forks may reduce the usable height. One should then measure the distance between stump height and usable height.
A Merritt rule for measuring tree heights can be inscribed on the reverse side of the Biltmore stick; then both rules, one for measuring tree diameter and the other for measuring tree height, will be on the same stick.
To inscribe the Merritt rule on the stick, simply mark graduations of 6.1 inches from the zero end of the stick (see Fig. 1). Each graduation represents a 16foot log length. Inscribe halflog marks halfway between the 16foot log marks. Make the graduation for both the diameter scale and the height scale with a sharp pencil or marker. Then give the stick a coat of clear var nish or polyurethane. This will bring out the color of the indelible lead, as well as protect the stick from moisture and discoloration.
Measure tree heights with the Merritt rule by the following method (see Fig. 3):
1. Stand 66 feet from the base of the tree. Hold the stick vertically at a distance of 25 inches from your eye.
2. Adjust the stick so that the zero end is in the line of sight with the upper limit of usable height.
3. Without moving your head or the stick, shift your line of sight to the stump height at the base of the tree (usually 12 to 16 inches above ground level). From the scale, read the number of logs (or fractions of logs) in the tree.
If the ground is not level, stand on a spot that has about the same elevation as the base of the tree.
Determining Tree Volume
After the diameters and heights of the trees have been measured, the board foot content for each tree can be read from a volume table. Board foot volume is estimated in many ways. Because many of these calculations were developed before the benefit of calculators, estimations are simplified formulas that are easy to tabulate by hand. Other, later formulas are more complex but ultimately more accurate in estimating the amount of useable wood. The International log rule (Table 2), one of these more recent estimation systems, gives a very accurate measure of the amount of lumber that a sound, straight tree will yield at the sawmill.
Local customs, however, sometimes require using other log rule calculations when standing timber is sold. Estimated volumes from two other log rules, Doyle and Scribner Decimal C, are given in Tables 3 and 4.
If you are going to fell the trees yourself and haul the logs to the mill, read the board foot values in Table 2, the International rule. However, if you are selling standing trees in the Lower Peninsula (and if the buyer insists), use the values in Table 3. If your trees are in the Upper Peninsula and the buyer demands it, use the values based on the Scribner Decimal C rule (Table 4).
In using these tree volume tables, increase the volumes by 10 percent for the following trees: balsam fir, spruce, white oak, yellow poplar, black cherry, beech and ash. Also, make suitable deductions for visible defects, such as rot.
Diameter 4 ½ feet above ground (inches) 
Number of 16foot logs


1 
2 
3 
4 

Volume in board feet 

10 
35 
60 


11 
45 
75 


12 
55 
90 
120 

13 
65 
110 
145 

14 
80 
130 
175 

15 
90 
155 
200 

16 

180 
240 
285 
17 

205 
280 
330 
18 

235 
315 
375 
19 

265 
360 
425 
20 

295 
400 
480 
21 

330 
450 
540 
22 

370 
500 
605 
23 

405 
550 
665 
24 

440 
605 
725 
25 

485 
665 
800 
26 


725 
880 
27 


790 
950 
28 


850 
1,030 
29 


920 
1,110 
30 


990 
1,070 
Diameter 4 ½ feet above ground (inches) 
Number of 16foot logs


1 
2 
3 
4 

Volume in board feet 

10 
15 
20 


11 
20 
30 


12 
30 
45 
50 

13 
40 
60 
70 

14 
50 
75 
95 

15 
60 
95 
120 

16 

115 
150 
170 
17 

140 
180 
210 
18 

165 
215 
250 
19 

195 
255 
300 
20 

225 
295 
350 
21 

260 
345 
400 
22 

295 
390 
460 
23 

330 
445 
520 
24 

370 
495 
580 
25 

415 
560 
660 
26 


620 
740 
27 


685 
815 
28 


750 
890 
29 


825 
980 
30 


900 
1,070 
Diameter 4 ½ feet above ground (inches) 
Number of 16foot logs


1 
2 
3 
4 

Volume in board feet 

10 
3 
4 


11 
4 
6 


12 
5 
8 
10 

13 
6 
9 
12 

14 
7 
11 
15 

15 
8 
14 
18 

16 

16 
21 
25 
17 

18 
25 
29 
18 

21 
28 
33 
19 

24 
32 
38 
20 

27 
36 
43 
21 

30 
41 
49 
22 

34 
46 
55 
23 

37 
51 
61 
24 

41 
56 
66 
25 

45 
62 
74 
26 


68 
81 
27 


74 
89 
28 


80 
96 
29 


86 
104 
30 


93 
112 
*The figures shown in this table must be multiplied by 10 to obtain board foot values.