California Big Trees - How to Measure a Tree
The California Register of Big Trees uses American Forests' points formula to determine whether a tree is a champion.
Trunk circumference in inches
+ Height in feet
+ ¼ of the average crown spread in feet
= Total Points
To measure the tree's circumference, measure around the tree at 4-½ feet above the ground on the tree's uphill side. If the tree forks below or bulges at 4-½ feet, measure the circumference where the tree reaches normal size or tapers below the 4-½ foot point. For accurate measurement, use a diameter tape or regular tape measure.
Measure the height from the ground level to the highest point. You can measure height with an instrument such as a laser hypsometer, clinometer, or abney level.
To find the tree's average crown spread, measure the widest point and the narrowest point of the crown. Add them together and divide by two to calculate the average crown spread.
American Forests Tree Measuring Guidelines
Measuring Guidelines Handbook - A complete guide to accurate measurements.