Tree Basal Area Calculator
Calculate the basal area of a tree from its diameter at breast height (DBH). Basal area is the cross-sectional area of the trunk at 1.3 m (4.5 ft) above ground, and it's a key measure in forestry for stand density and growth. Optionally enter trees per area to get the basal area per hectare.
Formula
Basal Area = π × (DBH ÷ 2)²
- Basal area is the cross-sectional area of a tree trunk at breast height (1.3 m / 4.5 ft).
- With DBH in centimetres, BA in m² = π × (DBH ÷ 200)².
- A quick metric shortcut: BA (m²) ≈ 0.00007854 × DBH(cm)².
- Basal area per hectare (the sum of all trees' basal area in a hectare) is a standard measure of stand density and stocking.
30 cm DBH tree
Inputs
- Diameter at Breast Height (DBH): 30 cm
- Trees per Hectare: 0 trees/ha
BA = π × (30 ÷ 200)² = π × 0.15² ≈ 0.0707 m² (about 707 cm²). With, say, 400 trees/ha of this size, the stand basal area would be about 28.3 m²/ha.
Frequently asked questions
What is basal area?
Basal area is the cross-sectional area of a tree trunk measured at breast height (1.3 m above ground). For a stand, it's the combined basal area of all trees, usually expressed per hectare or per acre.
What is DBH?
DBH stands for diameter at breast height — the trunk diameter measured 1.3 m (4.5 ft) above the ground. It's the standard input for basal area and many forestry calculations.
Why is basal area useful?
It's a simple, robust measure of how much growing space trees occupy. Foresters use basal area per hectare to assess stand density, decide on thinning, and track growth over time.
How do I get basal area per hectare?
Calculate the basal area of an average tree and multiply by the number of trees per hectare, or sum the basal area of every measured tree in the plot and scale to a hectare.