A felled log is heavier than almost everyone expects, and it is worth less lumber than almost everyone hopes. This log weight calculator answers both questions from the three measurements you can actually take in the woods: the diameter at the small end, the length, and how fast the stem tapers. It returns the solid wood volume, the green weight, and the sawn yield under the three log rules that mills in North America still scale by — Doyle, Scribner and International ¼-inch.
Arb Digital publishes free calculators for the trades, and this one exists because the weight number changes decisions. It decides whether a log can be lifted with the loader you have, whether a trailer is legal, and whether a single stem is a two-person job or a machine job. Every figure below is an estimate built on measurements you supply and species properties you look up. It is not a scale ticket and it is not a rigging plan.
What This Log Weight Calculator Does
It treats the log as a truncated cone between the small end and the large end and works out its solid volume by Smalian's formula — the average of the two end areas multiplied by the length. From that volume and a density derived from the species specific gravity and moisture content, it gives the green weight in pounds, in short tons and in kilograms.
Alongside the weight it runs the three common log rules so you can see how far apart they are. That gap is the single most useful thing on this page. The same 16-inch by 16-foot log scales at 144 board feet by Doyle and about 200 by International ¼-inch. Doyle is 28 per cent below International on that log, or to put it the other way, International is 39 per cent above Doyle — on identical wood, purely because the rules were drawn up at different times with different assumptions about saw kerf and slab loss.
This is a different job from our board foot calculator, which converts the dimensions of already-sawn, dressed lumber into board feet and cost. That tool starts with a rectangular board. This one starts with a round log and has to guess what a saw will get out of it. The cord of wood calculator answers a third question again — how much stacked firewood a pile represents — and none of the three substitute for one another.
How to Use It
- Measure the small-end diameter inside bark. Take two readings at right angles and average them, because logs are rarely round.
- Enter the length in feet. Log rules are tabulated for whole even lengths; mills usually add a trim allowance of a few inches which is not scaled.
- Set the taper, or measure the large end and enter it directly to override the taper estimate.
- Look up the specific gravity and green moisture content for your species in the Wood Handbook and enter them. These two numbers, not the geometry, are where most of the error in a weight estimate lives.
- Set the number of logs if you are estimating a load rather than a single stem.
The Formula and How It Is Calculated
Volume. Smalian's formula gives V = ((Asmall + Alarge) ÷ 2) × L, where each area is πd² ÷ 4 with the diameter converted from inches to feet. For a 16-inch small end, 0.5 inches of taper per 4 feet over a 16-foot log, the large end is 18 inches, the two areas are 1.396 and 1.767 square feet, and the volume is 25.31 cubic feet.
Density. The Wood Handbook relation for density at a given moisture content is ρ = 62.4 × SG × (1 + MC ÷ 100) pounds per cubic foot, where SG is the specific gravity on a green volume basis. At SG 0.45 and 80 per cent moisture that is 62.4 × 0.45 × 1.8 = 50.5 lb/ft³, so the example log weighs 25.31 × 50.5 ≈ 1,279 lb — well over half a ton for one 16-foot stick.
Doyle rule. BF = ((D − 4) ÷ 4)² × L. It subtracts four inches for slab and kerf and then squares, which is why it penalises small logs so heavily. A 16-inch, 16-foot log gives ((16−4)/4)² × 16 = 144 board feet.
Scribner rule. Scribner is a diagram rule: it was drawn by hand, laying out boards on a circle, and it has no exact algebraic form. The standard published approximation is BF = (0.79D² − 2D − 4) × L ÷ 16, which for the same log gives about 166 board feet. Where a scale ticket exists, the mill's Scribner table governs, not this formula.
International ¼-inch rule. This one is computed properly rather than approximated. The log is divided into 4-foot sections, each section scaled as 0.22d² − 0.71d, with a half-inch of taper added to the diameter of each successive section moving up from the small end. For the 16-inch, 16-foot example the four sections scale at 16, 16.5, 17 and 17.5 inches, totalling about 200 board feet. The rule assumes a quarter-inch saw kerf, which is why it is generally regarded as the most accurate of the three.
Why the Three Log Rules Disagree So Much
The rules are not three attempts at the same calculation. They are three different historical bargains between a seller and a buyer, and they encode different assumptions about saw technology. Doyle dates from an era of thick circular saws and heavy slabbing, and its flat four-inch deduction is a fixed penalty that hurts a 10-inch log far more than a 30-inch one. On small logs Doyle can underestimate real yield by half. On very large logs it starts to overestimate.
Scribner was drawn for boards laid out on a circle and reflects the geometry of what a sawyer could actually cut, but the hand-drawn tables contain irregularities that no formula reproduces exactly. International ¼-inch was derived mathematically with a defined kerf and a defined taper allowance, and it tracks actual mill output more closely than either older rule.
Which one applies is not a technical question — it is contractual. Mills in different regions buy on different rules, and the same wood is worth a different amount depending on which is written into the sale. If you are being paid by the board foot, find out which rule before you find out the price.
Where the Weight Estimate Goes Wrong
Geometry is the accurate part of this calculation. The error is almost entirely in the density inputs. Green moisture content varies enormously — between species, between sapwood and heartwood in the same stem, between seasons, and between a tree felled last week and one that has been lying since spring. A softwood sapwood can carry well over 100 per cent moisture by dry weight, meaning more than half its green weight is water.
That is why this page takes specific gravity and moisture content as inputs rather than publishing a species table. Getting them from the Forest Products Laboratory rather than from memory is the difference between an estimate you can act on and a guess. The dry weight figure in the summary line applies the same density relation at your target moisture content and deliberately ignores volumetric shrinkage, so it slightly overstates the volume of the dried piece.
Bark is the other quiet error. Log rules and this calculator work inside bark, but a log on a scale weighs with its bark on, and bark can be a meaningful fraction of the gross weight on a thick-barked species. If you are checking a calculated figure against a weigh ticket, that difference will show up.
Turning Weight Into a Handling Decision
A weight figure is only useful next to a capacity figure. Loader and crane capacities fall off with reach, trailer axle limits are legal limits rather than engineering ones, and a chain or sling has a working load limit that is a fraction of its breaking strength. None of those numbers are on this page and none of them should be estimated. The rated capacity of the specific machine, at the specific radius, and the rated working load of the specific rigging are what govern, and lifting is planned by a competent person.
For the general density-to-mass arithmetic on other materials, our material weight calculator covers metals, concrete and aggregates. If you are measuring standing timber rather than cut logs, the tree diameter calculator converts circumference at breast height to DBH and basal area, and the tree height calculator handles the height side of a volume estimate.
The authoritative free reference for wood density, specific gravity and moisture relations is the Forest Products Laboratory's Wood Handbook: Wood as an Engineering Material, published by the USDA Forest Service. For log scaling practice, grading and the regional differences between rules, the state extension forestry services publish plain-language guidance — NC State Extension Forestry is a good starting point.
Arb Digital builds websites and local search visibility for businesses that sell to a region rather than the world. If people nearby are searching for what you do and finding someone else, that is a fixable problem.
SEO Services Web Design ServicesCommon Mistakes to Avoid
- Measuring the large end because it is easier to reach. Every log rule scales from the small end; using the butt diameter overstates yield badly on a tapered stem.
- Measuring outside bark. Scaling diameters are inside bark, and on a thick-barked species the difference is several inches of apparent diameter.
- Assuming board feet from one rule equal board feet from another. They are different units of account, and a 16-inch log scales 28 per cent lower by Doyle than by International ¼-inch.
- Using an air-dry density for a freshly felled log. Green wood can be more than half water by weight, and a dry figure can understate the real weight by a third or more.
- Treating an estimated weight as a lifting plan. Machine capacity at reach, rigging working load limits and ground conditions decide what can be lifted, not a volume calculation.
Related Free Tools From Arb Digital
Convert sawn lumber dimensions with the board foot calculator, measure a firewood stack with the cord of wood calculator, work out density-based mass with the material weight calculator, appraise a standing tree with the tree value calculator, and convert bulk volumes with the cubic yard calculator. Browse the full free online tools hub, or contact us if a calculator you need is missing.
Frequently Asked Questions
It depends on volume and on the species density at its current moisture content. A 16-inch by 16-foot log of moderately dense wood at 80 per cent moisture works out at roughly 1,280 pounds. Enter the specific gravity and moisture content for your species to get a figure that means something.
Whichever the buyer scales by. Doyle, Scribner and International ¼-inch are contractual conventions rather than competing estimates of truth, and the rule written into the sale decides what the wood is worth. International ¼-inch generally tracks actual mill output most closely.
Doyle subtracts a flat four inches from the diameter for slab and kerf before squaring, which is a fixed penalty that falls hardest on small logs. On a 16-inch log Doyle scales about 28 per cent below International ¼-inch, which is the same as saying International scales 39 per cent above Doyle.
Under the bark, at the small end, averaged from two measurements taken at right angles. Log rules are all defined on diameter inside bark, and measuring over bark inflates the scale.
Because a species density typed from memory is worth nothing. Specific gravity and green moisture content are published for hundreds of species in the Forest Products Laboratory Wood Handbook, and this page takes them as inputs so the figure you get is traceable to a source.
No. A log rule estimates yield under assumptions about kerf and slabbing. Actual output depends on the mill, the sawyer, the sawing pattern, and defects like sweep, rot, knots and metal that no scaling formula can see.
No. It is a volume-and-density estimate for planning and transport awareness only. Lifting is governed by the rated capacity of the specific machine at the specific radius and the working load limits of the specific rigging, planned by a competent person.
Figures on this page are estimates derived from the measurements and species properties you supply, for planning and education only. They are not a scale ticket, a valuation or a lifting plan. Log scaling for sale is done under the rule written into the contract by a qualified scaler, and any lifting, loading or transport decision must follow the equipment manufacturer's rated capacities, rigging working load limits and the applicable transport regulations.
