Tree Basal Area Calculator
Basal area is the cross-sectional area of a tree trunk at breast height, a foundational measure in forest inventory and stand management. Enter the diameter at breast height (DBH) in inches and this calculator returns the single-tree basal area in square feet using the standard US forestry constant 0.005454 (which is pi/4 divided by 144). It also reports the trunk radius and the cross-sectional area in square inches, letting you check the conversion and use the result in stand density and volume estimates.
Tree basal area formula
Basal area (sq ft) = 0.005454 * DBH^2
where 0.005454 = (pi / 4) / 144
Cross-section (sq in) = (pi / 4) * DBH^2
Radius (in) = DBH / 2
DBH is the diameter in inches at 4.5 feet above ground. The constant converts a diameter in inches to a circular area in square feet. Diameter must be positive.
Forestry context
- DBH in the US is measured 4.5 feet above ground on the uphill side of the tree.
- The constant 0.005454 is standard in US Forest Service inventory procedures.
- Summing individual basal areas across a fixed area gives stand basal area per acre, a density metric.
- A 12-inch DBH tree has a basal area of about 0.79 square feet.
- For metric work, basal area in square meters equals 0.00007854 times DBH squared (DBH in centimeters).
Tree basal area: frequently asked questions
What is tree basal area?
Basal area is the cross-sectional area of a tree trunk measured at breast height (4.5 feet above ground in the US), expressed in square feet. It is a core forestry metric used to describe stand density and the space occupied by tree stems.
What is the formula for basal area from DBH?
Basal area in square feet equals 0.005454 times DBH squared, where DBH is the diameter at breast height in inches. The constant 0.005454 converts square inches to square feet and includes the factor of pi/4 used to turn a diameter into a circular area.
Where does the 0.005454 constant come from?
It is (pi / 4) divided by 144. Pi over 4 converts diameter squared into area for a circle, and dividing by 144 converts square inches to square feet (since 144 square inches make a square foot). The result, 0.0054542, is the standard US forestry basal-area factor.
What is DBH?
DBH stands for diameter at breast height, the standard point at which tree trunk diameter is measured, 4.5 feet (1.37 meters) above the ground in US forestry practice. It is usually measured with a diameter tape or calipers.
How is basal area used in forestry?
Stand basal area, the sum of all individual tree basal areas per acre, indicates stand density and competition. Foresters use it to schedule thinnings, estimate volume, and assess habitat. This calculator gives the basal area of a single tree.
Official sources
- USDA Forest Service: Forest Inventory and Analysis Program.
- National Institute of Standards and Technology: SI Conversion Factors.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.