Forestry

Forest Stand Metrics Quick Calculator

Check stem density and the density gap quickly from plot area, current stems, and target density.

If you know the initial stems, survival rate is included. If you paste DBH values, basal area and QMD appear on the same screen.

The main aim is to answer whether the stand is too dense and how many stems need to be added or removed as quickly as possible.

Plot-based Stem density Basal area Survival rate

All inputs stay in this browser and are never sent to a server.

How to use

Enter the plot area and current stems.
Choose the target density and unit system.
Add initial stems and optional DBH values when available.
Review current density, density ratio, supplementation or thinning, basal area, and QMD.
Copy, share, or print the result for notes and reports.

Samples

Supplement check for 0.05 ha

Input

Area 0.05 ha, current stems 44, initial stems 50, target density 1,000 stems/ha, DBH 12 cm x 44 trees

Output

Current density 880 stems/ha / density ratio 88% / supplement needed 6 stems / survival rate 88.0% / plot basal area 0.50 m² / basal area 9.95 m²/ha / QMD 12.0 cm

Thinning check for 0.25 acre

Input

Area 0.25 acre, current stems 44, initial stems 48, target density 160 stems/ac, DBH 5 in x 44 trees

Output

Current density 176 stems/ac / density ratio 110% / thinning candidates 4 stems / survival rate 91.7% / plot basal area 6.00 ft² / basal area 24.00 ft²/ac / QMD 5.0 in

Formulas

The calculator normalizes area, density, and diameters first, then shows the derived values.

Target stems in plot = ceil(plot area × target density)
Current density = current stems ÷ plot area
Density ratio = current density ÷ target density
Supplement needed = max(0, target stems - current stems)
Thinning candidates = max(0, current stems - target stems)
Survival rate = current stems ÷ initial stems
QMD = sqrt(Σ dbh² ÷ n), only when DBH values are present
Plot basal area = Σ [π × (dbh / 2)²]

Glossary

DBH

Tree diameter measured at breast height.

Stem density

The number of trees per unit area.

Basal area

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

QMD

Quadratic mean diameter derived from basal area and stem density.

Survival rate

Current stems divided by initial stems.

Supplement needed

The additional stems required to reach the target.

Thinning candidates

The stems above target that may be removed.

FAQ

Can I use it without DBH values?

Yes. Area, current stems, target density, and initial stems are enough. DBH values are only needed for basal area and QMD.

What happens if the current stem count does not match the DBH list length?

The tool shows a warning and keeps the entered stem count as the main value. The DBH list count is shown as a secondary check.

How does it switch between supplementation and thinning?

If the stand is below target, it shows supplement needed. If it is above target, it shows thinning candidates.

Can I mix units?

Yes. Area, density, and DBH units can be changed independently, and values are converted when you switch units.

Is anything sent to a server?

No. Calculation and local saving stay inside this browser.

Important notes

Use this as a quick check, not as the final basis for inventory decisions or stand treatment.
Keep every DBH value on the same height standard and in the same unit.
Area and density units are independent, and switching them converts the stored values too.
Shared URLs can contain your inputs, so narrow the sharing scope when needed.