Diameter at breast height
n. Diameter of a tree stem at a height 4.5 ft above ground level.
Diameter at breast height (DBH), unless otherwise noted, is measured outside the bark (DBHOB). On sloping terrain, DBH is measured 4.5 feet above the highest ground around the tree.
DBH is can be measured by ocular estimate or using tools such as a Biltmore stick, calipers, or diameter tape (d-tape). DBH of very large trees is estimated by dividing the circumference (outside bark) by pi (3.14159).