Tree Stand Volume & Timber Cruise Calculator

Calculate Stand Volume

Timber Cruising and Stand Volume

What Is Timber Cruising?

Timber cruising is the forestry practice of estimating the volume of harvestable wood in a stand of trees. A cruise involves measuring sample trees (Diameter at Breast Height or DBH, heights, species) and extrapolating to estimate total stand volume in board feet. Cruising is essential for forest management decisions: harvesting planning, timber sales, environmental impact assessment, and determining rotation age. Professional foresters use systematic sampling (fixed plots, line plots, point sampling) to achieve statistical accuracy; landowners and timber buyers rely on cruise estimates to negotiate pricing, plan operations, and allocate forest resources.

Key Timber Measurements

Diameter at Breast Height (DBH): Measured at 4.5 feet above ground level (standardized for comparison). DBH correlates strongly with tree volume: larger DBH trees contain exponentially more usable wood. A 24-inch DBH tree contains roughly 3–4× the volume of a 12-inch DBH tree.

Tree Height: Total height or merchantable height (height to a minimum 8-inch diameter top for commercial use) affects volume calculations. Height is typically estimated using clinometers or hypsometers; exact measurement in the field is challenging.

Merchantable Volume: Only the usable portion of the tree is counted—typically from DBH height to the top 8-inch diameter. Butt logs (lowest section) are highest quality; upper logs progressively lower quality. Waste and defects reduce merchantable volume by 5–30% depending on quality and species.

Timber Stand Volume Formula

where BF_total is total board feet, A_acres is stand acreage, N is trees per acre, V is board feet per tree (derived from DBH and height), and F_quality is a quality adjustment factor (0.7–1.0 representing waste, defects, and usability).

Board Feet Calculation from DBH and Height

The Scribner or International ¼-inch log scale are standard volume tables used in North America. For a rough approximation, the formula `BF ≈ 0.4 × DBH² × (Height ÷ 16)` provides estimates within ±10%. For example, a 16-inch DBH, 60-foot tall softwood tree: `0.4 × 16² × (60 ÷ 16) ≈ 0.4 × 256 × 3.75 ≈ 384 board feet`.

Worked Example: 10-Acre Softwood Stand Cruise

A 10-acre Douglas fir stand in Oregon with typical characteristics:

• Stand area: 10 acres
• Tree density: 80 trees per acre (typical for mature stand)
• Average DBH: 14 inches (mixture of ages)
• Average height: 60 feet
• Trees per tree volume (Scribner): ~80 BF per tree
• Quality/waste factor: 0.85 (15% waste due to defects, rot)
• Total volume: 10 acres × 80 trees/acre × 80 BF/tree × 0.85 = 54,400 board feet
• Average per acre: 5,440 board feet/acre (typical for this stand type)

Comparison Table: Board Feet Per Tree by DBH and Height

Board feet estimates using Scribner log scale (North American standard). Actual values vary by exact species, form, and merchantable height.

Timber Stand Quality Factors

Excellent Quality (Factor 0.95–1.0): Mature stand, minimal defects, sound wood, clear boles (straight trunk sections). Average timber sale price is highest for excellent quality.

Good Quality (Factor 0.85–0.90): Mixed-age stand, some defects, moderate quality wood. Most commercial stands fall in this category.

Fair Quality (Factor 0.70–0.80): Young trees or heavy defect load (rot, disease, storm damage). Lower-grade wood often suitable only for pulpwood or lower-value products.

Cruise Sampling Methods

Fixed Plot Method: Establish 1/10-acre or 1/5-acre circular plots randomly throughout the stand; measure all trees in each plot; extrapolate to full stand. Typically 3–5 plots per 10 acres.

Line Plot Method: Walk parallel lines through the stand, measuring trees within a fixed distance of the line; extrapolate linearly. Less labor-intensive than fixed plots.

Point Sampling (Angle Gauge): Using a calibrated angle gauge, count visible trees at each sample point; produces volume estimates per acre. Efficient but requires experience and equipment.

Timber Value Estimation Beyond Volume

Volume (board feet) is the foundation, but timber value depends on current market prices (volatile, $300–$800 per thousand board feet for softwood lumber; $600–$2,000 for hardwood, depending on species and grade). A stand with 100,000 BF might be worth $30,000–$160,000 depending on species, quality, market conditions, and harvest logistics. Stand accessibility (road access, slope, water barriers) affects harvest costs and final net value to the landowner.

Limitations and Professional Cruising

• This calculator provides rough estimates. Professional timber cruises by certified foresters achieve ±5–10% accuracy using statistical sampling and field measurements.
• Species-specific volume tables (available from state forestry agencies) provide more accurate estimates than generic formulas.
• Defect assessment requires field experience; visual inspection misses interior rot and quality issues.
• Height estimation without specialized equipment (clinometer, laser hypsometer) introduces ±5–15% error.
• Market prices for timber fluctuate; consult current regional prices for value estimates.
• Harvest costs vary greatly by accessibility; difficult-to-access stands cost more to harvest, reducing net value.
• For significant timber sales (>50 acres or >100,000 BF), professional cruise estimates are essential for negotiating fair prices.

Professional Consultation Recommendation

Landowners considering timber harvests should hire a registered/certified forester to conduct a cruise, assess sustainability, and represent their interests in timber sales negotiations. Foresters are trained in species identification, defect assessment, and market-level valuations. Their fees ($300–$1,000+ depending on stand size) are often recouped through better pricing in timber sales and optimization of sustainable harvest practices.