Why DBH matters
Diameter at breast height (DBH) is one of the standard measurements used in forest inventory, timber estimation, basal-area calculations, and stand-density work.
In U.S. forestry practice, DBH is commonly measured outside bark at 4.5 feet above the ground, generally from the uphill side on sloping ground. Circumference can be converted to diameter using diameter = circumference ÷ π. University of Minnesota Extension provides a practical overview of tree measurement.
Basal area per tree
The calculator also reports basal area using the standard forestry relationship BA = 0.005454 × DBH², where DBH is in inches and basal area is square feet; this coefficient is used in USDA Forest Service inventory work.
Measurement note: Butt swell, forks, deformities, leaning stems, and unusual ground conditions can require special DBH measurement rules. Follow the inventory protocol used for your project.