Log Board Foot Calculator

Estimate how many board feet of lumber a log contains using the three standard U.S. log rules: Doyle, Scribner and International ¼-inch.

Log Measurements

Measure inside the bark at the small end of the log. Logs are rarely round, so averaging two measurements taken at right angles gives a fairer diameter.

Extra lumber a sawmill typically gets beyond the log scale. Leave at 0 if you don't know it.
Estimated Board Feet
16" × 16 ft, 1 log
International ¼"closest to actual lumber yield
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Scribnerformula approximation
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Doylelowest for small logs
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How Many Board Feet Are in a Log?

It depends on the log's small-end diameter, its length and the log rule used. A 16-foot log with a 12-inch small end scales 95 board feet by the International ¼-inch rule, 80 by Scribner and 64 by Doyle (Purdue Extension).

Log rules estimate the lumber you can saw from a log after losses to saw kerf, slabs and taper. That's why they give less than the log's full cylinder volume.

Board Feet in a 16-Foot Log by Diameter

Published values for 16-foot logs, as listed in Purdue Extension's Log and Tree Scaling Techniques:

Small-end diameterDoyleScribner (Decimal C)International ¼"
8 in 16 30 40
10 in 36 60 65
12 in 64 80 95
14 in 100 110 135
16 in 144 160 180
18 in 196 210 230
20 in 256 280 290
24 in 400 400 425

Scribner Decimal C rounds to the nearest 10 board feet. Published tables round values, so the calculator's formula results can differ from them by a few board feet.

The Three Log Rule Formulas

D is the small-end diameter inside bark in inches, L is the log length in feet:

Doyle

BF = (D − 4)² × L ÷ 16

Developed around 1825, it allows a 4-inch slabbing allowance, about twice the normal amount, so it underestimates small logs and overestimates large ones (Virginia Cooperative Extension). It gives lower volumes than the International rule for logs up to about 30 inches.

Scribner

BF ≈ (0.79D² − 2D − 4) × L ÷ 16

The original Scribner rule (about 1846) is a diagram rule. It was drawn by fitting 1-inch boards into circles the size of log ends, with no allowance for taper, so it tends to underestimate long logs. The formula above is a common approximation of it (Purdue Extension).

International ¼-Inch

BF = 0.905 × (0.22D² − 0.71D) for each 4-foot section

Developed in 1906 with a ¼-inch saw kerf and a taper allowance of ½ inch per 4 feet of length, it is the most consistent of the three. It's the one to use when you want to estimate actual lumber output. For a 16-foot log, the sections add up to about 0.796D² − 1.375D − 1.23 (Purdue Extension; WOODWEB). The calculator adds the 4-foot sections one by one, widening the diameter by ½ inch each time.

Why the Rule Matters When You Sell Logs

A price per thousand board feet (MBF) means nothing until you know which rule it's based on. The same 12-inch, 16-foot log is 64 board feet by Doyle and 95 by International. At $500 per MBF that's $32 versus about $48 for the same log. Before comparing offers from buyers, ask which log rule each one uses. Use the price field above to see the value under all three rules at once.

How to Measure a Log

  1. Measure the small end, inside the bark. Take two measurements at right angles and average them.
  2. Be consistent with fractions. Decide in advance how you round. Always rounding down lowers the scale.
  3. Measure length with a tape, don't estimate it. A log just short of a whole foot is tallied at the shorter length, and trim allowance matters.
  4. Watch for swollen ends. Logs cut through branch stubs or flared areas can measure an inch or more bigger than the diameter you can actually mill.

Measuring guidance from Purdue Extension FNR-191. Scalers also deduct for defects such as rot, sweep and splits, which this calculator does not.

Overrun: Lumber Beyond the Scale

Overrun is the extra lumber a mill saws beyond what the log rule predicted, as a percentage (underrun is the opposite). It depends on the log rule, log size and taper, species, kerf and sawing equipment. Mills that buy logs usually know their typical overrun and build it into their price. To estimate lumber output, Purdue Extension recommends the International rule with an adjustment for expected overrun. If you know your mill's figure, enter it in the calculator.

Frequently Asked Questions

How many board feet are in a 20-inch, 16-foot log?

About 256 by Doyle, 280 by Scribner and 290 by International ¼-inch, according to Purdue Extension's tables.

How do I estimate board feet in a standing tree?

Foresters estimate the usable logs in the tree's merchantable height and scale each log. For a rough number after felling, measure each log's small end and length and add up the results from this calculator.

Why does the Doyle rule give so little for small logs?

It subtracts 4 inches from the diameter before squaring it, a generous slab allowance. On a 10-inch log that leaves only 6 inches to work with, so Doyle shows about half of what the International rule does.

How is this different from a lumber board foot calculator?

Log rules predict how much lumber a round log will yield. For boards that are already sawn, use our board foot calculator, which works from thickness, width and length.

Note: Log rule results are estimates. Actual yield depends on defects, sawing pattern and equipment. For timber sales, use the rule and scaling practices your buyer or state specifies.

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