Log Board Foot Calculator
Compare Doyle, Scribner, and International 1/4 inch scales for one log.
How to measure
Measure the small end inside the bark
Take the diameter at the small end, inside the bark, in inches. Measure the narrow way across the end, then the measurement at a right angle, and average the two. Scribner rounds that average to the nearest inch before it reads the table, and the result names the inch it used. Do not measure the large end, and do not include the bark. A log that is out of round can differ by an inch between those two readings, which is enough to change the scale.
Measure length in feet
Enter the log length in feet. Commercial logs are usually an even number of feet, plus a trim allowance the scale does not count. Lengths over 20 feet are normally scaled as two or more segments, because the International formula and the Scribner table were built for one log of that length or shorter. Count the logs that share this diameter and length, and enter a price per thousand board feet only when you want a value.
Formula
Doyle subtracts 4 inches from the small-end diameter, squares what is left, multiplies by the length in feet, and divides by 16. A result that would go negative is shown as zero. Scribner Decimal C reads a published table when the rounded diameter and the length in whole feet are both on the table. Otherwise it uses the Bruce and Schumacher formula and marks the result approximate. International 1/4 inch uses the Grosenbaugh formula and then rounds to the nearest 5 board feet.
The percent under each rule is that rule minus International, divided by International. It is a comparison, not a third scale.
A 16 inch by 16 foot log is 144 board feet by Doyle, 160 by Scribner Decimal C, and 180 by International 1/4 inch. The International formula before rounding is 180.6.
Common mistakes
- Measuring the large end, or measuring outside the bark.
- Treating a Doyle scale on a small log as the lumber a mill will saw. Doyle runs low under about 20 inches.
- Reading Scribner without rounding the diameter to a whole inch.
- Scaling a log longer than 20 feet as one piece.
- Entering a price per board foot in the value field. That field is dollars per thousand board feet.
FAQ
How many board feet are in a log?
It depends on the scale rule, and the three common rules do not agree. A 16 inch log that is 16 feet long is 144 board feet by Doyle, 160 by Scribner Decimal C, and 180 by the International 1/4 inch rule. The International figure is the formula rounded to the nearest 5 board feet. Enter the small-end diameter, the length, and the number of logs, and this page shows all three.
Why do Doyle, Scribner, and International disagree?
Doyle subtracts 4 inches and squares what is left, so small logs come out low and large logs come out high. Scribner is a diagram rule, published as the Decimal C table in tens of board feet. International allows for saw kerf and a little taper, and it is the closest of the three to the lumber a mill can saw. The percent under each card is that rule compared with International.
Which log rule should I use?
Use the rule the buyer uses. Doyle is common on private timber in the East and the South. Scribner was the Forest Service rule in the Lake States and the West, and many mills still scale with it. International is the most accurate of the three and the least used in trade. This page shows all three so you can see the spread before you agree a price.
Where do I measure the diameter?
Measure inside the bark at the small end. Take the narrow way across the end and the measurement at a right angle, then average the two. Scribner rounds that average to the nearest inch before it reads the Decimal C table, and the result names the inch it used. Do not include the bark, and do not measure the large end. The diagram on this page draws a schematic large end only.
What does the Scribner approx. label mean?
The Decimal C table covers whole-foot lengths from 4 to 20 feet and diameters from 6 to 40 inches. When the length is a whole foot inside that range, the page reads the table and labels the result as the table. Outside that table the page uses the Bruce and Schumacher formula and marks the result approximate. A length that is not a whole foot always uses the formula.
How is the log price calculated?
Enter dollars per thousand board feet, written MBF. Value is the scale, times the number of logs, times that price, divided by 1,000. Each rule gets its own value because each rule produces a different scale. Leave the price blank if you only want board feet. The page does not divide again, so do not enter a price that is already per board foot.
Related tools
- Price sawn boards in board feet Price sawn boards, with waste and lumberyard tally.
- Compare Doyle and Scribner Why the three log rules diverge on small logs and large ones.
- Convert board feet to linear feet Turn a board-foot total into the lineal feet to order.
- Pack the scale onto stock lengths Pack these boards onto stock lengths before you buy.
By Lumber Calc Editorial Team · Verified against 2021/2024 IRC & AWC DCA 6 · Last updated Oct 24, 2026