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Log Board Foot Calculator — Doyle, Scribner & International Log Scale

Enter small-end DIB and length. Get board feet under Doyle, Scribner, or International 1/4" — side by side.

Log Scale Calculator
Diameter + Length
Doyle / Scribner / International
6 in12 in30 in

Measure at the small end, inside the bark. The scale tallies DIB to the nearest inch.

Gross log scale estimate · Doyle

64

Board feet

12 in DIB → 12 in scale diameter 16 ft nominal length Doyle: nearest 1 BF
Show rule comparison

Scribner: 80 BF · Int'l: 95 BF

Quote, defect & tally

1 logs · no quote · 0% deduction

Which of these three numbers do you use?

Use the rule your buyer, mill, or contract names — not the highest board-foot figure. Same cut log, different named scale, different number.

Doyle subtracts a fixed 4 inches before it scales. On small logs that cut is a large share of the diameter, so Doyle often reads lower than Scribner or International 1/4-inch. The wood in the log did not change.

A $/MBF quote is only comparable when both sides name the same scale, the same DIB method, and the same length convention.

Use it this way and you can:

  • Estimate one cut log or a full tally under a single named rule
  • Compare Doyle, Scribner, and International on the same inputs
  • Apply an optional defect deduction and a $/MBF quote without mixing scales

For cut logs you can measure. It does not grade defects for you, predict a mill's recovery, or scale standing trees.

How do you measure a log for board feet?

Wrong spot or wrong end throws the estimate off. Measure small-end DIB, then length, then pick the rule your buyer names.

LengthDIBLarge EndSmall EndMeasure
Tip: If the bark is thick or rough, measure inside bark (DIB) when you can.
  1. 1

    Where do you measure diameter?

    Small end, inside the bark (DIB). Outside-bark diameter usually runs high — especially on thick bark.

  2. 2

    What length do you enter?

    Usable length in feet (often 8–20 ft). Match the nominal length the mill will scale.

  3. 3

    Which log rule do you pick?

    Use the rule your buyer, mill, or contract names. Chasing the highest BF is not the same as matching the quote.

Which log rule should you use?

Each rule reports a gross board-foot estimate. The same log can scale differently — pick the one named on the deal.

Doyle Log Rule

How it calculates
BF = (D − 4)² × L ÷ 16, rounded to the nearest 1 BF. D = small-end DIB (in); L = nominal length (ft).
Use when
Your buyer, mill, or local market quotes Doyle — common in parts of the eastern and southern U.S.
Watch for
The fixed 4-inch allowance usually scales small logs lower than Scribner or International 1/4-inch.

Scribner Log Rule

How it calculates
Tally DIB to the nearest inch, pick the nominal length, then read the published Scribner Decimal C short-log table value — do not re-round it.
Use when
Your buyer, mill, or sale contract names Scribner Decimal C — common in many western U.S. timber markets.
Watch for
It is a table, not a continuous formula. An approximate equation may not match the published value.

International 1/4-Inch Rule

How it calculates
Apply the International 1/4-inch formulas (1/4-inch kerf + taper assumptions), then round gross scale to the nearest 5 BF.
Use when
Your contract names International 1/4-inch, or you want a comparison under its stated kerf and taper assumptions.
Watch for
More detail still does not predict a particular mill's recovery or replace the scale used on the deal.

Want the full derivation, history, and more examples? Read the log-scaling guide .

What happens when you try these inputs?

Same scale contract as the calculator. Run the numbers yourself — rule choice and tally math, not mill yield or whether a local price is fair.

Why does an 8" × 16' log scale so differently by rule?

One small cut log. Seller and buyer need to see what changes when they name a different rule.

Enter these inputs

  • DIB: 8 in at the small end, inside bark
  • Nominal length: 16 ft
  • Defect deduction: 0%

Calculator output

Why does an 8" × 16' log scale so differently by rule?
Doyle16 gross BF
Scribner Decimal C30 gross BF
International 1/4-inch40 gross BF
Why the result differs
Doyle's fixed 4-inch allowance hits small diameters hard. Scribner reads a published Decimal C table. International 1/4-inch uses different kerf and taper assumptions.
What it means
The log did not gain wood. A higher BF figure alone does not make an offer better.
Takeaway
Before comparing $/MBF, name the same rule, DIB method, length convention, and deduction basis.
Boundary
Gross scale for these inputs only — not mill recovery, not hidden defects.
Use these inputs in the calculator

How does a six-log Scribner tally become a $/MBF total?

A load with repeated sizes. Keep one scale, total the BF/MBF, then apply a quote already named in that scale.

Enter these inputs

  • 2 × 10 in DIB × 16 ft = 60 gross BF each
  • 3 × 14 in DIB × 12 ft = 90 gross BF each
  • 1 × 20 in DIB × 12 ft = 210 gross BF
  • Scale: Scribner Decimal C; quote: $500/MBF; defect deduction: 0%

Calculator output

How does a six-log Scribner tally become a $/MBF total?
Total logs6
Gross total BF600 BF
Gross total MBF0.600 MBF
Estimated value at $500/MBF$300.00
Why the result differs
Every row uses the same selected scale from its DIB, length, and quantity. 600 BF becomes 0.600 MBF, then the quote applies.
What it means
One convention for the whole load — easy to export, copy, or print without mixing scales.
Takeaway
If a buyer quotes another scale, recalculate the full load under that scale before comparing price.
Boundary
$300.00 is only for this $500/MBF Scribner example — not a fair-price call or a yield promise.
Use these inputs in the calculator

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

The search is only a diameter. Length and the named scale still have to be stated.

Enter these inputs

  • DIB: 20 in at the small end, inside bark
  • Nominal length: 16 ft (the calculator's default length)
  • Defect deduction: 0%

Calculator output

How many board feet are in a 20-inch log?
Doyle256 gross BF
Scribner Decimal C280 gross BF
International 1/4-inch290 gross BF
Why the result differs
A 20-inch small-end DIB still needs a length. These three figures are 16-foot logs under each named rule.
What it means
There is no single board-foot count for "a 20-inch log." Change the length or the rule and the number changes.
Takeaway
State DIB, nominal length, and the named scale before you treat the figure as a quote.
Boundary
Gross scale for 20 in × 16 ft only — not mill recovery, not a standing tree.
Use these inputs in the calculator

What measuring mistakes throw off the scale?

Most bad estimates start with the wrong diameter, the wrong end, or the wrong rule.

!

Did you measure outside the bark?

Most rules assume DIB at the small end. Outside bark overestimates — especially on thick-bark species.

!

Did you measure the large end?

Use the small end. The large end inflates the estimate because logs taper.

!

Are you comparing quotes under different rules?

Confirm Doyle, Scribner, or International 1/4" before you compare BF or $/MBF numbers.

When should you use a different page?

I have sawn boards, not a log

Thickness, width, and length of lumber use the board-foot calculator, not a log rule.

Board Foot Calculator

I want the formulas and more worked examples

The log-scaling guide walks through Doyle, Scribner, and International with extra tables.

Log-scaling guide

What this calculator does not do

This is a gross log-scale estimate for information only — not a mill-recovery promise. Any defect % you enter is your assumption. The tool does not detect defects or replace professional grading. Species, taper, kerf, and local practice change recovery. Confirm the rule, DIB vs outside bark, and rounding with your buyer or mill.

Sources