Log Weight Calculator

Pick up a green oak log and you will quickly discover that wood is mostly water. A freshly cut 18-inch Red Oak log 14 feet long weighs over 4,000 lbs — more than a small car. That weight comes from two things: the volume of the log and the density of the species at its current moisture level.

This calculator treats the log as a cylinder. Volume equals pi times the radius squared times the length. The radius is half the mid-point diameter, converted from inches to feet. That volume in cubic feet is then multiplied by the species density figure — a pounds-per-cubic-foot average for that species at the moisture state you selected. The result is the estimated weight in pounds and tons.

Species density figures are averages compiled from timber engineering references. Individual trees vary based on site quality, growth rate, and age. Fast-grown plantation timber is typically less dense than old-growth timber of the same species. The tool uses mid-range published averages, which are reliable enough for hauling, lifting, and structural planning but not for precision engineering where material testing is required.

Use this calculator when you need to decide whether a log or log pile can be safely moved, lifted, or hauled with equipment you have available. It is the right tool for checking whether a skidder, forklift, crane, or truck can handle the load before you commit. It is also useful for estimating firewood pile weight, rough milling yield planning, and budgeting timber transport costs that charge by the ton.

This calculator is also helpful when sizing rigging equipment for a tree removal. Knowing that a 16-inch oak section 8 feet long weighs roughly 1,300 lbs lets you select the right sling rating before the cut is made.

Do not use this calculator as a substitute for certified weight tickets when legal weight compliance is required — for example, for road permits or commercial timber contracts. Do not use it for precision structural engineering. And do not use it for logs with unusual conditions: heavy rot, major hollow sections, extensive charring, or severe taper beyond 3 inches over the log length will push real weight outside the formula's reliable range.

The most common mistake is measuring diameter at the large end instead of the midpoint. Because volume scales with radius squared, a 24-inch large end on a log that is actually 18 inches at mid-length produces a 78 percent overestimate of volume. Always measure at the midpoint, or take both end measurements and average them.

A second mistake is ignoring moisture state. A green Sitka Spruce log can weigh 30 percent more than the same log after six months of air drying. Using air-dried density figures for a freshly felled log will significantly underestimate hauling weight, which matters when you are within 10 percent of a truck or crane limit.

The third common error is using this estimate for structural load calculations without safety margin. This tool gives a planning-level number. Real timber structures require certified species grading, actual moisture testing, and engineered load analysis. The cylinder formula is accurate for hauling and rough planning — it is not a substitute for a licensed structural engineer when lives depend on the result.

The core formula is: Weight = pi x (diameter / 24)^2 x length x density

Diameter is divided by 24 because diameter is in inches and needs to become a radius in feet — divide by 2 to get radius, then divide by 12 to convert inches to feet. Squaring that gives the cross-sectional area in square feet. Multiplying by length in feet gives cubic feet. Multiplying by density in lbs per cubic foot gives weight in pounds.

Board feet by Doyle scale follow a separate formula: ((diameter - 4) squared times length) divided by 16. This formula was derived empirically in the 19th century and still dominates US hardwood trading. It assumes significant saw kerf and slab waste and tends to undercount yield on logs under 14 inches in diameter. For softwood timber, the Scribner scale is more common in the western US, but Doyle is used here as the default because it is more widely recognized for hardwood species.

The cylinder formula assumes a constant circular cross-section, which no real log has. Taper alone causes the formula to overestimate volume by 10 to 25 percent on typical sawlogs. Professional timber scalers use the Smalian or Huber formula — which average the end cross-sections or measure the true midpoint area — to reduce taper error. The Doyle board foot scale used here also breaks down below 14-inch diameter: it can undercount actual yield by 40 percent on a 10-inch log, which is why some portable sawmill operators use the International 1/4-inch rule instead for small-diameter logs.