Optional Laboratory: Calculating Board Footage In A Tree
- How much lumber comes from one tree?
- How many trees did it take to build the house or apartment you live in?
- Measure the height of the tree you are studying.
- Measure the diameter of the tree you are studying. Make sure you write these two measurements down very carefully on the data sheet.
- Remember the formula to find the area of a circle is (A=r
^{2}x p). Area = radius squared times 3.14). Since a tree is almost circular, use this formula to find the area of your tree at DBH (diameter at breast height). Since the formula requires the radius of the tree and you just measured the diameter, divide the diameter by 2. Dividing the radius by 12 converts inches to feet. - Now use this number to calculate the area of your tree.
- Don't relax now! We are only beginning! Use the formula in step 5 of the data sheet to find out how many cubic feet of lumber are in your tree.
Cubic Feet = Area (ft) X Height (ft) / 4 (note: 4 is used to account for the taper of the tree) - There are 12 board feet of lumber for every one cubic foot, so multiply cubic feet by 12. You have calculated how many board feet of lumber your tree has.
- Practice on several other trees to get comfortable with this series of calculations.
- Your teacher may have already measured and calculated board footage for the trees. Compare your own measurements with your teachers.
Tree # _____ - Height _____ feet
- Diameter _____ inches
- Diameter in feet / 2 = ________ radius in inches / 12 = _____ feet
- Area of tree cross-section = above number squared x 3.14 =______ sq.ft.
- Volume of tree in cubic feet = above number x tree height / 4 = ______
- Volume of tree in board feet = above number x 12 = _________
Tree # _____ - Height _____ feet
- Diameter _____ inches
- Diameter in feet / 2 = ________ radius in inches / 12 = _____ feet
- Area of tree cross-section = above number squared x 3.14 =______ sq.ft.
- Volume of tree in cubic feet = above number x tree height / 4 = ______
- Volume of tree in board feet = above number x 12 = _________
Tree # _____ - Height _____ feet
- Diameter _____ inches
- Diameter in feet / 2 = ________ radius in inches / 12 = _____ feet
- Area of tree cross-section = above number squared x 3.14 =______ sq.ft.
- Volume of tree in cubic feet = above number x tree height / 4 = ______
- Volume of tree in board feet = above number x 12 = _________
Tree # _____ - Height _____ feet
- Diameter _____ inches
- Diameter in feet / 2 = ________ radius in inches / 12 = _____ feet
- Area of tree cross-section = above number squared x 3.14 =______ sq.ft.
- Volume of tree in cubic feet = above number x tree height / 4 = ______
- Volume of tree in board feet = above number x 12 = _________
- Gain experience at measuring tree heights and tree diameters.
- Understand the standard unit of measurement for lumber.
- Calculate the board footage of a given tree using a formula.
- Relate the number of trees needed to build a small house.
When a tree diameter is taken, make sure it is a true DBH. DBH (Diameter at breast height) is measured at 4.5 feet from the ground on the tree trunk. When a tree is on a slope, the 4.5 feet is measured on the up slope side of the trunk. When students have made both tree measurements and are ready to plug numbers into the formula, make sure they use the radius measurement in feet. The measurement they took was in inches, so it must be converted into feet. For example, if a student measured a tree's diameter to be 14 inches, the radius would be 7 inches and the number to used in the formula would be 0.58 feet. (7 / 12 = 0.58) A fairly straight pine tree is an ideal tree for this exercise.
- A small ranch style house with 3 bedrooms (approximately 1000 square feet) would require about 3000 board feet of lumber to build. Have students arrive at the number of trees that would be needed to build the house they presently live in. Have the students make this calculation from their data (originally measured trees).
- Conifers are the trees of choice for construction lumber. Have students research the products that are made from oaks, hickories and ashes.
*Earth's Trees: Environmental Learning Series.*WP Press, Tucson, Arizona. 1992.*Illinois Council on Forestry Development.*A Long Range Plan for Illinois Forest Resources. 1990.*Elements Of Forestry: With Special Reference to Illinois.*Department of Conservation, Division of Forestry, Springfield, Illinois. 1973.
Tree # An Example of How Midwest Lumber Is Used
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