Tree Diameter Calculator
Find tree diameter from its circumference.
Convert a tape-measured trunk circumference into diameter (DBH).
How the Math Works
The Tree Diameter Calculator uses the fundamental relationship between a circle's circumference and its diameter. Since all circles follow the ratio where circumference equals diameter times pi (C = d π), we can rearrange this formula to solve for diameter: diameter = circumference ÷ π. This means you simply divide the measured circumference of the tree trunk by the mathematical constant pi (approximately 3.14159) to find the exact diameter, giving you a precise measurement without needing to cut through the tree.
Practical Applications
To use this calculator in practice, first measure the tree's circumference at breast height (typically 4.5 feet or 1.37 meters above ground level) using a measuring tape or a piece of string that you can later measure. Once you have the circumference measurement in the same units (inches, centimeters, etc.), enter it into the calculator or divide by pi manually. This method works for any tree shape since circumference measurements can wrap around irregular trunks, and the formula accounts for the circular approximation inherent in diameter calculations.
Day-to-Day Use
This calculation is valuable for foresters, arborists, and tree enthusiasts who need to estimate tree size, age, and health without invasive procedures. Property owners can use it to determine if trees exceed planting boundaries, calculate lumber quantities, or assess storm damage impact. Environmental scientists track forest growth patterns, while homeowners estimate shade coverage and pruning needs. The quick, non-destructive measurement helps with tree care decisions, insurance documentation, and urban planning without requiring specialized equipment beyond a simple measuring tape.
Worked example
38 in around → 12.1 in DBH.
FAQ
Where to measure?
At breast height — 4.5 ft above the ground.