Board Foot Calculator for Logs

How much lumber is in a log? Foresters and sawmills estimate it with log rules — formulas that convert a log’s small-end diameter and length into board feet. This calculator applies the three most common US rules side by side, totals a whole tally of logs, and also works out board feet for sawn lumber, so you can compare what a buyer quotes with what you might saw.

What is a board foot?

A board foot is a volume of wood 12 inches long, 12 inches wide and 1 inch thick — 144 cubic inches. A 1 × 8 inch board 10 feet long is 1 × 8 × 10 ÷ 12 = 6.67 board feet. Log rules estimate how many board feet of lumber a log will yield after sawing, allowing for the round shape, bark, saw kerf and slabs, which is why the answer is always much less than the log’s total volume.

The three common log rules

Which rule applies depends on your region and buyer — always ask which rule a mill or forester uses.

Worked example: one log, three rules

The same log is worth up to about 25% more board feet under the International rule than under Doyle. For smaller logs the gap is much larger: a 10-inch, 12-foot log scales about 27 board feet under Doyle but about 46 under International ¼-inch.

How to measure a log

1. Measure the diameter at the small end, inside the bark, to the nearest inch.
2. If the end is oval, average the longest and shortest diameters.
3. Measure length in feet; most rules assume even lengths (8, 10, 12, 14, 16 ft) plus a few inches of trim allowance.
4. Note defects — rot, splits, sweep, knots — which reduce the net scale.
5. Record each log on a tally sheet.

Selling logs and timber

• Ask which log rule the buyer uses and whether prices are per thousand board feet (MBF).
• Hardwood sawlog prices vary greatly by species, grade and location — get more than one quote.
• A consulting forester can mark and scale a timber sale and often increases the landowner’s return.
• Veneer-quality logs are priced far above sawlogs; don’t let them go as firewood.

Defects and deductions

Gross scale assumes a sound, straight log. Scalers deduct for defects that reduce usable lumber: rot at the ends or in the centre, splits and shakes, sweep and crook, large knots and metal such as nails or fence wire in yard trees. Deductions are often estimated as a percentage of the gross scale or by reducing the effective diameter or length. The tally sheet includes columns for gross board feet, deductions and net board feet.

Tree volume versus log volume

Standing trees are estimated differently: foresters measure diameter at breast height (4.5 ft above ground) and count the number of 16-foot logs up to a merchantable top, then read volume from tree tables built on the same log rules. A log calculator like this one is used once trees are felled and bucked into logs, or to check a buyer’s scale ticket.

Sawing your own lumber

If you mill logs with a portable sawmill, expect your yield to be closest to the International ¼-inch rule for a thin-kerf bandsaw, and lower for a chainsaw mill with a wide kerf. Air-dry lumber stickered and covered, allowing roughly a year per inch of thickness as a rough rule for many hardwoods, and remember that drying shrinks boards slightly.

Lumber board feet

For sawn lumber, board feet = thickness (in) × width (in) × length (ft) ÷ 12. Rough hardwood is sold by nominal quarter thickness: 4/4 (1 in), 5/4, 6/4, 8/4 (2 in). Softwood dimensional lumber (2 × 4, 2 × 6) is usually sold by the piece or linear foot, but board feet let you compare prices across sizes.

Printable log scale pack

The optional pack includes printable Doyle and International ¼-inch log scale tables (diameters 8–36 in, lengths 8–16 ft), a log tally sheet and a lumber board-foot worksheet. The calculator above is free.

AI-assisted content

This page was drafted with AI assistance and reviewed by Kedop. Log rules give estimates; actual yield depends on the log, defects, the mill and the sawyer.