Measuring Tree Diameter and Height

March 12, 2006

Trees are in part valued on their volume. To determine the volume of a tree the diameter and the height of the tree must be measured.

A flexible measuring tape can be used to measure the diameter. The diameter of a tree is measured at breast height, which is defined as 4.5 feet above the ground on the uphill side of the tree. The circumference of the tree is what you will measure by wrapping the tape around it, making sure there are no kinks in the tape and the tape does not sag. To convert the circumference at breast height to the diameter at breast height (dbh), divide by 3.14. For example if the circumference is 82", dividing by 3.14 will yield a result of 26", therefore the dbh of the tree is 26".

A measuring tape and two sticks of equal length can be used to measure the height of a tree. Find the center point on one of the sticks, hold the other stick perpendicular to it, effectively making the letter "T". Step away from the tree until you can see the top and bottom. Put the base of the "T" between your eyes, then walk away or toward the tree until the top and bottom of the stick line up with the top and bottom of the tree. Make a mark on the ground, the distance between your mark and the tree is the total height of the tree, if you are on flat ground. If you are on sloped ground, the slope distance will need to be converted to horizontal distance.

These are exercises for interested persons that do not have the tools of the forestry trade available to them. Foresters use diameter tapes, biltmore sticks and relaskops to measure diameter and height, or their eye to discern diameter and height more efficiently.

I welcome responses as well as ideas for future Tree Tips. You can also get an email version by contacting me at thembi@mcn.org.

Thembi Borras is a Registered Professional Forester living and working in Mendocino County, CA USA.