Calculate Cubic Feet Of Wood Log

Wood Log Volume Calculator

Estimate the solid wood volume of a round log using diameter, length, form factor, and bark deduction. This premium calculator also shows cubic meters, approximate board foot equivalent, estimated weight, and a chart that visualizes how volume changes with diameter.

Log inputs

Formula used: cubic feet = π × radius² × length. Radius is half the diameter after converting to feet. Net cubic feet = gross cubic feet × form factor × (1 – bark deduction ÷ 100).

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Tip: If you are estimating logs for sawing, the calculator gives a solid volume estimate, not an official timber sale scale. Mill recovery, taper, defect, and trim allowance can all reduce usable lumber output.

How to calculate cubic feet of a wood log accurately

When people search for a way to calculate cubic feet of wood log, they usually want a fast answer for one of three reasons: pricing timber, planning firewood or milling output, or estimating transport weight. Cubic feet is one of the most useful volume measurements because it describes the actual three dimensional size of the wood. Unlike a board foot, which is tailored to lumber thickness assumptions, or a cord, which includes air space in a stacked pile, cubic feet focuses on solid volume. That makes it a practical baseline for comparing logs of different sizes, species, and uses.

The core idea is straightforward. A log can be approximated as a cylinder. If you know the diameter and the length, you can estimate volume using the cylinder formula. In imperial units, the standard approach is to convert the diameter into feet, divide by two to get the radius, square the radius, multiply by pi, and then multiply by the log length in feet. The result is gross cubic feet. From there, you can refine the estimate by applying a form factor for taper and a bark deduction if you want a more realistic net wood volume.

This page calculator is designed for practical field use. It lets you enter different units, apply a realistic form factor, and estimate dry weight based on species density. If you are buying logs, comparing standing timber, planning trailer loads, or trying to understand how much wood a tree stem actually contains, cubic feet gives you a common language that works across many situations.

The basic log volume formula

The standard cylinder formula is:

1. Convert diameter to feet.
2. Radius = diameter ÷ 2.
3. Cross sectional area = π × radius × radius.
4. Volume = cross sectional area × length in feet.

Written compactly, the formula is:

Cubic feet = π × (diameter in feet ÷ 2)² × length in feet

Suppose a log measures 18 inches in diameter and 12 feet in length. Convert 18 inches to feet by dividing by 12, which gives 1.5 feet. The radius is 0.75 feet. Then:

• Area = 3.1416 × 0.75 × 0.75 = about 1.767 square feet
• Volume = 1.767 × 12 = about 21.21 cubic feet gross

If you apply a form factor of 0.90 for normal taper and a 5 percent bark deduction, the net solid wood estimate becomes:

21.21 × 0.90 × 0.95 = about 18.13 cubic feet

This kind of adjustment matters because real logs are rarely perfect cylinders. The narrower small end, surface irregularities, and bark thickness all affect usable solid wood volume.

Why cubic feet matters for forestry, milling, and firewood

Cubic feet is helpful because it bridges the gap between forestry measurements and practical wood use. A mill may eventually think in board feet. Firewood sellers may think in cords. Haulers may care more about gross vehicle weight. Yet all of these decisions improve when you first know the log volume in cubic feet.

Common uses for cubic foot calculations

• Timber valuation: Cubic volume helps compare stems before selecting a log scale or sale method.
• Sawmill planning: A rough board foot equivalent can be estimated from cubic feet, though recovery varies by species and defect.
• Equipment sizing: If you know cubic feet and wood density, you can estimate the load weight for trailers, tractors, or skidders.
• Firewood conversion: Cubic feet can help you compare solid wood against stacked volumes such as a face cord or full cord.
• Inventory management: Landowners and arborists can quickly estimate how much material is on site after harvesting or storm cleanup.

What cubic feet does not tell you by itself

• It does not automatically account for defects such as rot, sweep, crook, or hollow sections.
• It does not guarantee a board foot yield, because sawing pattern and kerf affect recovery.
• It does not represent a stacked firewood cord directly, because a cord includes voids between split pieces.

That is why this calculator distinguishes gross volume from a more realistic net estimate. The gross number is useful as a geometric benchmark. The net number is often better for planning and pricing.

Comparison table: common log sizes and gross cubic feet

The table below uses the cylinder formula with no taper adjustment and no bark deduction. These are gross values and make a helpful reference for quick field estimates.

Diameter	Length	Gross Cubic Feet	Approx. Board Foot Equivalent
12 in	8 ft	6.28 cu ft	75 bd ft
12 in	16 ft	12.57 cu ft	151 bd ft
16 in	10 ft	13.96 cu ft	168 bd ft
18 in	12 ft	21.21 cu ft	254 bd ft
20 in	12 ft	26.18 cu ft	314 bd ft
24 in	16 ft	50.27 cu ft	603 bd ft

The board foot values above use a simple volumetric relationship of roughly 12 board feet per cubic foot. Real sawmill output can be lower or higher depending on diameter, taper, slab loss, and sawing practice, so treat these as broad approximations rather than official scale numbers.

How species affects estimated log weight

After finding cubic feet, many users want to know how much the log weighs. Weight matters for transport, loader capacity, trailer selection, and safety. Weight depends heavily on species and moisture content. Green wood is substantially heavier than dry wood, and dense hardwoods are much heavier than light softwoods. The calculator above provides a dry weight estimate based on common species averages.

Species	Approx. Dry Density	Estimated Weight of 20 cu ft Log	Typical Use
Eastern White Pine	25 lb per cu ft	500 lb	Light framing, interior work
Douglas-fir	33 lb per cu ft	660 lb	Structural lumber, beams
Southern Yellow Pine	35 lb per cu ft	700 lb	Treated lumber, framing
Black Walnut	37 lb per cu ft	740 lb	Furniture, cabinetry
Red Oak	44 lb per cu ft	880 lb	Flooring, furniture, millwork
Hickory	50 lb per cu ft	1000 lb	Tool handles, high wear uses

These values are practical averages rather than absolute constants. If a log is freshly cut and still green, total weight can be significantly higher. For transport planning, always build in a safety margin.

Best practices for measuring a wood log

1. Measure diameter carefully

Diameter is the most sensitive input in the formula because volume rises with the square of the radius. A small measurement mistake can produce a surprisingly large error. In many forestry settings, log diameter is measured inside bark at the small end for more consistent scaling. If you are measuring outside bark, a bark deduction can help bring the estimate closer to solid wood volume.

2. Measure merchantable length, not total visual length

If the butt end is flared, the top is damaged, or trim allowance is needed, the usable length may be less than the full stem section. For saw logs, many buyers care about merchantable length in standard increments. For on site estimates, use the true usable length you expect to process.

3. Choose a realistic form factor

A perfect cylinder is a useful theoretical maximum, but natural logs taper. That is why the calculator allows a form factor. A very straight, uniform log may justify 0.95. A typical saw log often fits around 0.90. Rougher, more tapered stems may be closer to 0.85 or 0.80. If you are unsure, 0.90 is a practical middle ground.

4. Account for defects separately

If the log has major rot, a hollow center, severe crook, or significant end splits, the pure volume formula will overstate what you can use. In those cases, note the gross cubic feet first, then apply a separate defect reduction based on your experience or buyer specifications.

Cubic feet versus board feet and cords

Many misunderstandings happen because these units describe wood in different ways. Cubic feet measures solid volume. Board feet measure sawn lumber volume using a conventional thickness reference of one inch. Cords measure a stacked pile, usually 128 cubic feet, including air space between pieces. That means a cord is not the same thing as 128 cubic feet of solid wood.

• 1 cubic foot is a true volume cube measuring 1 foot by 1 foot by 1 foot.
• 1 board foot equals a board 12 inches by 12 inches by 1 inch, which is 1/12 of a cubic foot.
• 1 cord usually equals a stacked pile 4 feet by 4 feet by 8 feet, totaling 128 cubic feet of stacked space.

As a quick relationship, 1 cubic foot of solid wood is roughly equal to 12 board feet of raw wood volume. But actual lumber recovery depends on saw kerf, edging, taper, and waste. Likewise, converting solid cubic feet to cords requires assumptions about splitting, stacking, and air space.

Worked example for a real world estimate

Imagine you have a red oak log that is 20 inches in diameter and 14 feet long. It is fairly straight, so you choose a form factor of 0.90. Bark is moderate, so you apply a 6 percent bark deduction. Here is the process:

1. Convert diameter: 20 inches ÷ 12 = 1.667 feet
2. Radius: 1.667 ÷ 2 = 0.8335 feet
3. Area: 3.1416 × 0.8335² = about 2.182 square feet
4. Gross cubic feet: 2.182 × 14 = about 30.55 cubic feet
5. Net cubic feet: 30.55 × 0.90 × 0.94 = about 25.84 cubic feet
6. Approximate board foot equivalent: 25.84 × 12 = about 310 board feet
7. Estimated dry weight for red oak: 25.84 × 44 = about 1137 pounds

This single example shows why cubic feet is so useful. With one core volume estimate, you can reason about milling potential, material handling, and trucking needs.

Authoritative references for measurement and wood data

If you want to go beyond quick estimates and review official guidance on units, forest measurement, and wood properties, these sources are excellent starting points:

• National Institute of Standards and Technology unit conversion guidance
• U.S. Forest Service resources on forestry measurement and timber management
• Penn State Extension woodlot, timber, and forest product guidance

These references are especially helpful if you need more formal scaling methods, species data, or timber sale planning information.

Final takeaway

To calculate cubic feet of a wood log, start with diameter and length, convert both to feet, and apply the cylinder formula. Then improve the estimate by using a form factor and bark deduction. That gives you a practical net volume that is useful for forestry, milling, firewood planning, and transport decisions. Because diameter has the biggest effect on the answer, measure carefully and use consistent assumptions. If you need a quick but professional estimate, the calculator above provides a reliable, field friendly way to do it.