When selling lumber for commercial use, you must determine the volume of lumber in cubic meters to know the tree's worth. Because a tree's girth changes along the trunk, and because some of the tree is not usable lumber, you must apply a formula to make the calculation. To use the formula you’ll need to take a few measurements of the tree. With measurements in hand, just a few calculations will determine how much lumber you have.
Things You'll Need
 Tape measure
 Lath
 Pencil

Obtain the tree’s diameter at breast height by locating a point exactly 4 1/2 feet from the ground and wrapping a tape measure around the trunk at that point. Record the measurement. When measuring trees sitting on a slope, locate breast height by measuring up 4 1/2 feet on the uphill side of the tree.

Mark a piece of lath with a pencil line across its width every four inches. Move 50 feet from the center of the tree so that you can view the entire tree without it leaning toward or away from you. Hold the lath 25 inches in front of you and align the wood with the tree trunk. Position the wood so that the bottom appears to be about 1 foot from the tree's base. Count the number of 4inch marks that the tree rises along the stick. Record this number.

Multiply the number of marks the tree measured on your lath by 8 to estimate the merchantable height of the tree. This is the amount of commercially usable lumber the tree possesses.

Calculate the area of the tree at breast height by dividing the diameter at breast height by two, squaring that number, and then multiplying the result by 3.1415. Multiply the area by the merchantable height of the tree. Take the result and multiply by 0.7 to allow for the natural tree taper to get the cubic volume of the tree in feet. Multiply that by 12 to calculate the board feet of lumber available in the tree.

Divide the board feet of lumber by 424 to obtain the number of cubic meters of lumber in the tree.
References
 Photo Credit Jupiterimages/Photos.com/Getty Images