Basal Area and Stem Density Calculator Forestry Tools

Basal Area, Stem Density, and Average DBH Calculator

Calculate basal area, stem density, and average DBH (QMD) from fixed plot and BAF angle-gauge surveys.

Keep DBH, BAF, and QMD in a shared forestry vocabulary while switching between metric / imperial and mm / cm / in.

Supports fixed plot and BAF surveys Shows QMD as the primary average DBH Shares by URL, CSV, JSON, and print

Input

Settings
Settings

Result

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Basal area / area
—
Stem density
—
Average DBH (QMD)
—
QMD
Total tree count
—
Trees
Point count
—
Row results
Arithmetic mean DBH
—
Arithmetic mean DBH

Warnings

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Trees Basal area Stem density Arithmetic mean DBH QMD
--

Survey methods supported

Fixed plot

Use known plot area and DBH lists to calculate basal area per area and stem density.

BAF angle gauge

Use in-tree DBH lists and BAF to estimate basal area per area and stem density from point samples.

Average DBH is QMD

The primary average DBH is QMD, or quadratic mean diameter. Arithmetic mean DBH is shown as a secondary check when tree-level diameters are present.

Examples

Input / Output

How to use

  1. Switch the survey mode between fixed plot and BAF.
  2. Choose the unit system, DBH unit, and either plot area or BAF depending on the mode.
  3. Enter the DBH list for each plot or point. You can separate values with newlines, commas, semicolons, or spaces.
  4. Review basal area, stem density, and QMD, then use copy, CSV, JSON, share URL, or print when needed.

Frequently asked questions

Is average DBH the arithmetic mean?

The primary average shown by this tool is QMD. Arithmetic mean DBH is shown as a secondary check only when tree-level diameters are present.

Can BAF alone estimate stem density?

Yes. With DBH values entered, the tool estimates stem density from each in-tree's expansion factor.

Should DBH be measured at 1.3 m or 4.5 ft?

Either is fine as long as you use one consistent measurement standard for the values you enter. The tool does not auto-correct height standards.

Do you handle slope correction or boundary-tree rules?

No. The tool only aggregates the numbers after field tallying.

Can I share large row data through a URL?

Yes, but the URL can become long. Use JSON export and import for larger surveys.

Glossary

DBH

Diameter at Breast Height. Tree diameter measured at breast height.

Basal area

The cross-sectional area of tree stems at breast height.

Stem density

The number of trees per unit area.

QMD

Quadratic Mean Diameter. An average DBH derived from basal area and stem density.

BAF

Basal Area Factor. The factor used in angle-gauge surveys.

Fixed plot

A tally method using a plot with a known area.

Formulas

tree basal area = π × (dbh / 2)^2

basal area per area = Σ tree basal area / sample area

stem density = tree count / sample area

QMD = sqrt(4 × basal area per area / (π × stem density))

BAF row basal area = in-tree count × BAF

BAF row stem density = Σ (BAF / tree basal area)

Notes

  • DBH measurement height standards vary by country and stand. Make sure all values were measured using the same standard.
  • Follow your field tally rules for boundary trees when using BAF.
  • QMD is the primary metric. It may not match arithmetic mean DBH.
  • Do not put private stand names or trial-plot names into share URLs or notes.
  • The result is a summary value, not the final basis for legal, certification, or management decisions.