Basal Area Calculator
Enter a tree's diameter at breast height (DBH) and, optionally, the number of trees, to calculate basal area per tree and total stand basal area.
Last updated: September 25, 2026
Frequently asked questions
Can I enter trunk circumference instead of DBH?
Yes. Choose the circumference option, enter the girth you measured around the trunk at breast height, and the calculator converts it with DBH = circumference / π before computing basal area. This assumes the trunk cross-section is close to circular; buttresses, lean, and irregular trunks make circumference-based DBH less exact than a diameter-tape reading.
What is DBH and why is it measured at breast height specifically?
DBH (diameter at breast height) is a tree's trunk diameter measured at a standardized height of 4.5 feet (1.37 m) above ground. Measuring at a fixed height makes DBH consistent and comparable across trees and surveys, avoiding the flare and irregularity common near the base of a trunk.
What is basal area used for in forestry?
Basal area (the cross-sectional area of a tree's trunk at DBH) is a standard measure of how much of a site's area is occupied by tree stems - foresters use total stand basal area to assess stocking density, plan thinning, and estimate timber volume alongside tree height and form.
Where does the 0.005454 constant come from?
It's derived from the standard circle area formula (π/4), converted to work directly with DBH in inches and basal area in square feet: π/4 ÷ 144 (square inches per square foot) = 0.005454. This lets you go straight from a DBH measurement in inches to basal area in square feet without a separate unit conversion step.
How do I calculate total basal area for a stand with trees of different sizes?
Calculate basal area per tree individually for each DBH size class present, multiply each by its tree count, then sum the results - this calculator handles one DBH value (with a tree count) at a time, so a mixed stand needs one calculation per size class added together.
Is basal area the same as canopy area or crown area?
No - basal area is the cross-sectional area of the trunk at breast height, not the area covered by the tree's canopy or crown from above. The two aren't directly proportional, since crown spread depends on species, spacing, and growing conditions in ways trunk diameter alone doesn't capture.
What's a typical basal area for a well-stocked forest stand?
It varies substantially by forest type, region, and management goals, but many managed stands are targeted in the range of roughly 80-120 ft² of basal area per acre - consult species- and region-specific forestry guidelines for a stocking target relevant to your stand.