Tree Diameter Calculator

DBH is the standard forestry measurement of a tree's trunk diameter taken at breast height, typically 4.5 feet (1.37 meters) above ground in the United States. Different countries use slightly different heights: Australia, Canada, and Europe use 1.3 meters, Japan and Korea use 1.2 meters, and New Zealand uses 1.4 meters. DBH is used for estimating tree age, volume, biomass, and carbon storage.

Wrap a measuring tape tightly around the tree trunk at the DBH height (4.5 feet above ground). Record the measurement where the number 0 on the tape aligns with the rest of the tape. For trees on a slope, measure from the uphill side. For leaning trees, measure along the underside face of the trunk.

Diameter over-bark (DOB) is the diameter measured including the bark, which is what you get from a standard circumference measurement. Diameter under-bark (DUB) is the diameter of the wood alone, excluding bark thickness. DUB is calculated as DUB = DOB - (2 x bark thickness). Under-bark diameter is important for timber volume estimation and wood product calculations.

For multi-stemmed trees where the stems share a common root system, each stem is measured separately at breast height. The overall equivalent diameter is found using the quadratic mean: measure the circumference of each stem, calculate each stem's diameter, square each diameter value, add all squares together, and take the square root of the total. Our calculator performs this calculation automatically.

Most trees grow between 0.2 cm and 0.4 cm in diameter and between 1.5 cm and 2.5 cm in circumference per year. Growth rates vary by species, age, site conditions, and climate. Young trees in optimal conditions grow faster. Using Mitchell's Rule, every 2.5 cm of girth roughly represents one year's growth for many tree species.

DBH measurement height varies by country: the United States uses 4.5 feet (1.37 meters), Australia, Canada, and Europe use 1.3 meters (4.27 feet), Japan and Korea use 1.2 meters (3.93 feet), and New Zealand uses 1.4 meters (4.59 feet). Always use the standard for your region for consistent and comparable measurements.