To nominate a tree, you need three measurements: Trunk Circumference (inches), Height (feet), and Average Crown Spread (feet). Trees of the same species are compared using the following calculation:
Trunk Circumference (inches) + Height (feet) + ¼ Average Crown Spread (feet) = Total Points.
Tree-measuring Guidelines Handbook
With the guidance of the Measuring Guidelines Working Group, American Forests has released the National Big Tree Program’s tree-measuring guidelines handbook. This comprehensive guide was assembled and published to ensure accuracy and integrity in the national register of Champion Trees.
A tree must be re-measured at least every 10 years to maintain its champion status.
- 1. Measure the distance around the trunk of the tree, in inches, at 4 ½ feet above ground level. This point is called the diameter breast height (dbh).
- 2. If the tree forks at or below 4 ½ feet, record the smallest trunk circumference below the lowest fork. Record the height at which the measurement was taken.
Trees should be considered separate if the circumference measurement below the lowest fork places the measurement on the ground
- 3. If the tree is on a slope, measure 4 ½ feet up the trunk on the high and low sides of the slope. The dbh is the average between both points. If the tree is on a steep slope, take the measurement at 4 ½ feet above the midpoint of the trunk.
- 4. If the tree is leaning, measure the circumference at 4 ½ feet along the axis of the trunk. Make sure the measurement is taken at a right (90 degree) angle to the trunk.
Measure the vertical distance, in feet, between the base of the trunk and the topmost twig. Height is accurately measured using a clinometer, laser, hypsometer, or other specialized tools.
- 1. Find a
straight stick or ruler.
- 2. Hold the stick vertically at arm’s length, making sure that the length of the stick above your hand equals the distance from your hand to your eye.
- 3. Walk backward away from the tree. Stop when the stick above your hand is the same length as the tree.
- 4. Measure the distance from the tree to where you are standing. Record that measurement to the closest foot.
Two measurements of the crown spread are taken and recorded, in feet, at right angles to one another.
- 1. Measure the widest crown spread, which is the greatest distance between any two points along the tree’s drip line. The drip line is the area defined by the outermost circumference of the tree’s canopy where water drips to the ground.
- 2. Turn the axis of measurement 90 degrees and find the narrow crown spread.
- 3. Calculate the average of the two crown spread measurements using this formula: (wide spread + narrow spread)/2 = a
verage crown spread