Methods & limits

How the numbers are made.

The calculators are intentionally transparent. You can see the inputs, the unit conversion, the formula and the distinction between an exact volume and an estimate.

Board feet for finished lumber

With thickness and width in inches and length in feet, the calculator uses BF = thickness × width × length ÷ 12. When all dimensions are in inches, it uses division by 144. Metric inputs are converted to cubic metres and then to board feet using 1 board foot = 0.002359737216 m³.

Board feet from a round log

The log calculator compares the Doyle, Scribner approximation and International 1/4-inch rules. These are estimates of recoverable lumber, not the physical volume of the tree and not a guarantee of mill recovery.

Cords of firewood

A cord is a stacked volume, not a weight and not an amount of solid wood: 128 cubic feet of wood ranked and well stowed. The firewood calculator measures the stack you enter against that definition, then uses an explicit solid-wood assumption — a figure you can change — to derive weight and heat. Heat follows density, since a pound of ovendry wood carries about the same energy whatever the species; a species table is therefore a density table. The regulatory side of the same subject, including the states we have verified, is on firewood sale law.

Rounding and invalid rows

Totals use unrounded values and are formatted only for display. If one row is invalid, the total is withheld and export is disabled so a partial answer cannot look complete.

Sources

Each calculator page includes its method notes, assumptions and source references. If a method is an approximation, the page labels it as such.