Log Volume Calculator

Enter a log's small-end diameter and length and get its wood volume in board feet by the Doyle and International 1/4-inch rules, plus cubic feet and cubic metres.

Construction & DIYWorldwideSource: Briggs (1994), Univ. of Washington: log rule formulas and Appendix 3 tablesFree, no sign-up

Small-end diameter, inside bark (in)

Log length (ft)

Large-end diameter (in) (optional, for cubic)

Number of identical logs

The answer updates as you type; nothing is sent anywhere.

Board feet

95 BF International ¼″ · 64 BF Doyle

Cubic volume 12.57 ft³ (0.356 m³) as a cylinder at the small-end diameter — add the large end for Smalian’s formula.

Rule	Board feet	From
International ¼-inch	95	published table value
Doyle	64	published table value

The arithmetic

Doyle: ((d − 4) ÷ 4)² × L. International ¼″: 0.905 × (0.22d² − 0.71d) for each 4-ft section, with d growing ½ inch per section. Cubic: 0.005454 × d² × L for a cylinder, or 0.005454 × (d² + D²) × L ÷ 2 (Smalian).

What this page cannot tell you

Log rules estimate the lumber a sawmill might get, and the two rules disagree — most of all on small logs. Your sale uses whichever rule the buyer scales by, minus deductions for defects. This is gross scale only.

How to work out the volume of a log

Measure the small end. Measure the diameter inside the bark at the small end of the log, in inches. Log rules are built on this scaling diameter.
Measure the length. Enter the length in feet. The published tables cover 6 to 16 ft; other lengths use the rule's formula.
Add the large end for cubic volume. With both end diameters the cubic volume uses Smalian's formula; with only the small end it is treated as a cylinder.
Compare the rules. Read the board feet under both rules. They often differ a lot, especially for small logs.

10 situations where a log volume calculation helps

Checking a mill's tally before selling logs

A landowner can see the expected scale of a load under the rule the buyer uses, before the logs leave the property.

Seeing why Doyle pays less for small logs

On a 10-inch, 16-ft log, Doyle gives 36 BF and International 1/4-inch gives 65 BF. Knowing the gap matters when a sale is priced per thousand board feet.

Planning a portable sawmill job

An owner of a few storm-felled trees can estimate how much lumber the logs might yield.

Pricing a single walnut or oak log

Specialty buyers quote per board foot; the volume gives a starting figure for the conversation.

Turning cubic feet into firewood or weight estimates

The cubic volume is the starting point for weight or cord calculations.

Teaching timber measurement

Students can see the published table value next to the formula value.

Checking a load of identical logs

Entering the number of logs multiplies the scale for a uniform batch.

Comparing bucking choices

Running one long log against two shorter ones shows how the rules treat length and taper differently.

Estimating volume in metric

The cubic result is also given in cubic metres for buyers who work in metric.

Settling a disagreement about a log's size

Both parties can see the same published rule values.

Where the log rules come from

The formulas and tables are from David Briggs, Forest Products Measurements and Conversion Factors (College of Forest Resources, University of Washington, 1994), Chapter 2 'Measurement of Logs' and Appendix 3 'Board Foot Log Rules'.

Doyle: board feet = ((d − 4) ÷ 4)² × L, where d is the small-end diameter in inches and L the length in feet. Briggs explains it squares the log into a cant by taking 4 inches off the diameter, then deducts 25% for kerf and shrinkage, and notes it underscales small logs and overscales large ones. The formula, rounded to whole board feet, reproduces all 150 cells of the Appendix 3 Doyle table (6–30 in, 6–16 ft).

International 1/4-inch: the log is treated as 4-ft cylinders, each ½ inch wider than the last. Each cylinder holds 0.22d² − 0.71d board feet with a 1/8-inch kerf; the 1/4-inch rule is 0.905 times that. Rounded to the nearest 5 BF, this matches 147 of the 150 tabled values; the other three differ by one 5-BF step. So inside the table range the page shows Briggs's published value, and outside it the formula value, labelled. Briggs's text also prints the 1/4-inch cylinder as 0.20d² − 0.71d, but that does not reproduce his own example of 85 BF for a 10-inch, 20-ft log, so it is not used.

Cubic volume uses Briggs's Table 2-1: Smalian's formula 0.005454 × (d² + D²) × L ÷ 2 when both ends are entered, otherwise a cylinder at the small end. Briggs notes Smalian tends to overestimate butt logs. The Scribner Decimal C rule is a diagram rule without a formula and is not included.

Limits: this is gross scale. It makes no deductions for rot, sweep, crook or other defects, and it does not tell you what a mill will pay or actually saw. Everything is calculated in your browser.

Sources

Briggs (1994), Chapter 2: Measurement of Logs (PDF) — Doyle and International formulas; Table 2-1 cubic formulas
Briggs (1994), Appendix 3: Board Foot Log Rules (PDF) — Published International 1/4-inch and Doyle tables, 6–30 in × 6–16 ft

Frequently asked questions

How do you calculate the volume of a log?

Measure the small-end diameter inside the bark and the length. For board feet, apply a log rule such as Doyle ((d − 4) ÷ 4)² × L. For cubic feet, 0.005454 × d² × L treats it as a cylinder; Smalian's formula averages the two end areas.

How many board feet are in a 12-inch, 16-foot log?

The published tables give 95 BF by the International 1/4-inch rule and 64 BF by Doyle.

Why do Doyle and International give different answers?

Doyle deducts a flat 4 inches of diameter for slabs and edgings, which is a large share of a small log, so it gives far less on small logs. International models taper and kerf more closely.

Which log rule should I use?

The one your buyer uses. Doyle is common in the U.S. South, Scribner in the West, and International 1/4-inch in some other regions. This page does not choose one for you.

Do I measure the diameter with or without bark?

Inside the bark, at the small end. Log rules are built on the small-end scaling diameter.

How do I convert a log's cubic feet to cubic metres?

Multiply cubic feet by 0.0283168. The calculator shows both.

Does this calculator include Scribner?

No. Scribner is a diagram rule with no formula, so it is not reproduced here.