How to Figure Out the Circumference of a Tree

Measure a tree's circumference to approximate its age.

To figure out the diameter or even the age of a tree without cutting it down and counting the growth rings, you must measure its circumference. Circumference is the distance around a circular object. Most trees, especially mature ones, tend to flare out at the base of the trunk where it meets the ground. Measuring there won't give you an accurate measurement of its growth. Landscape professionals measure the circumference of a tree at chest height, 4.5 feet, to calculate its true diameter.

Things You'll Need

• Measuring tape
• Helper
• Piece of string (optional)
• Yardstick (optional)

Instructions

1. Ask your helper to stand on one side of the tree's trunk, holding one end of the measuring tape against the bark 4.5 feet above the ground.

2. Hold the other end of the tape and walk around the tree in a circle until you meet your partner back at the beginning. Take note of the measurement--this is the tree's circumference.

3. Use a piece of string if you don't have a measuring tape and follow Steps 1 and 2. Measure the string against a yardstick to find the tree's circumference in inches.

4. Measure the largest of the multiple trunks, if the tree trunk forks below 4.5 feet, at 4.5 feet to find the circumference in inches.

Tips & Warnings

• Calculate the diameter of the tree's trunk at chest height by dividing its circumference by 3.14 inches.

References

• Virginia Tech: How to Measure a Big Tree: Circumference
• University of Minnesota: Estimating Tree Diameter
• Oregon State University; How to Measure Trees; Mark Wilson; 2007

Resources

• Michigan State University; Tree Growth (Tree Age and Height); Christensen