Measuring a tree

Trees submitted as nominees for the Big Tree Registry must be measured with circumference in inches, and height and crown spread to the nearest foot. The total of these measurements is the points awarded to a particular tree.

Steps to measure a tree

How to measure a tree

1. Circumference

Get circumference by measuring the distance around the tree to the nearest inch at 4½ feet above the ground. A flexible tape measure is a good tool to use. Measure without pressing into deep convolutions or indentations on the tree.

Person measuring tree with tape measure.

How to find the circumference of hard-to-measure trees:

Measure trees with double stem

illustation showing a tree with a double stem and where to measure.

Tree with a double stem that forks below 4½ feet above the ground—measure at the narrowest place below the fork.

Measure trees with forks at ground level

illustation showing a tree with a double stem and where to measure.

Tree that has forks at ground level—measure the largest stem at 4½ feet.

Measure trees that have heaved.

illustation showing a tree that has heaved and where to measure.

When the base of a tree is "heaved" (tree roots exposed usually due to the effects of erosion, along with tree movement and growth patterns)—the measuring point begins where the root mass ends and the tree trunk begins.

Measure trees on a slope

illustation showing a tree on a slope and where to measure.

Tree growing on a slope—measure 4½ feet above the midpoint of the different ground levels.


2. Height

graphic: measuring height of treeHeight is the hardest measurement to get. The most reliable method uses a hand level or hypsometer. If these instruments are unavailable, use a ruler and follow the instructions below.

  1. On a 12" ruler, mark the 1" and 10" lines with tape.
  2. Have a partner stand at the tree’s base.
  3. Hold the ruler in front of your eyes at arm length and walk back until you see the whole tree from top to bottom between the 0" and the 10" marks on the ruler.
  4. Move your body forward and backward until the base of the tree is exactly at 0 inches and the top of the tree is exactly at 10".
  5. Sight out from the 1" mark to a point on the trunk above the base.
  6. Have your partner mark with tape that spot on the trunk.
  7. Measure the distance from the base of the tree to the tape mark.
  8. Multiply by 10 to get an approximate height of the tree.

3. Crown spread

  1. Setting a stake directly under the outside edge of the crown farthest from the trunk (A)
  2. Add another stake directly opposite it at the outer edge of the crown on an imaginary line passing through the tree’s center (B)
  3. Rotate 90 degrees and set stakes on outside edges of the crown passing through the center of the tree (C and D)
  4. Measure the distance between points (A) and (B)
  5. Measure the distance between points (C) and (D)
  6. Add the two measurements together and divide the sum by two to find the average crown spread. Average Crown Spread = [(Distance A to B) + (Distance C to D)] / 2
  7. Calculate one-quarter of the crown spread by dividing the average crown spread by four. One-quarter Crown Spread = Average Crown Spread / 4
diagram measuring the crownOne way to measure a tree's crown size - using one transect for the widest part of the crown and one for the narrowest part of the crown.

Awarding points

A champion tree has accumulated the most points based on the measured circumference, height, and crown spread. If two trees of the same species have close scores, co-champions will be crowned if:

  • The trees are under 100 points and within 3 points.
  • The trees over 100 points and their difference is within 3 percent of the total.

Example:

Measurements of tree:
Circumference = 120 inches
Height = 76 feet
Crown Spread = 40 feet

Figuring points:
Circumference = 120
Height = 76
Crown Spread = 40 ÷ 4 = 10
Total points = 120 + 76 + 10 = 206