Tree Diameter Calculator

in
Measured at 4.5 feet above ground (breast height).
Biology

Calculate a tree's diameter at breast height (DBH) from its trunk circumference, or vice versa.

Formula

DBH = Circumference ÷ π
  • Diameter at Breast Height (DBH) is measured at 4.5 feet (1.37 m) above ground.
  • Basal Area (sq ft) = π × r² ÷ 144.
  • Basal area is used in forestry to estimate timber volume per acre.

50-inch circumference tree

Inputs
  • Trunk Circumference: 50 in

DBH = 50 ÷ π ≈ 15.9 inches.

Frequently asked questions

Why is DBH measured at 4.5 feet?
4.5 feet (breast height) is a standardized measurement height for consistency across foresters.
What is a large tree DBH?
Generally trees with DBH > 20 inches are considered large; old-growth trees often exceed 36 inches.