Board-Foot Calculator: How Much Lumber Is in Your Log?

Q: How do I calculate board feet from a log?

Measure the small-end diameter in inches (inside the bark) and the log length in feet. Apply the Doyle formula: ((diameter − 4) ÷ 4)² × length. A 16-inch diameter, 12-foot log yields 108 board feet by the Doyle rule.

Q: What's the difference between the Doyle rule and the Scribner rule?

Both estimate board feet from a log's dimensions but use different formulas. The Doyle rule is dominant east of the Rockies and among portable sawyers; it tends to under-count small logs under 14 inches. The Scribner rule is more common in the Pacific Northwest and gives higher estimates for small logs. The difference on a single log can be 15–30%.

Q: How much does it cost to mill a log into lumber?

Most portable sawyers charge $0.25–$0.50 per board foot or $60–$125 per hour. A 16-inch oak log 12 feet long yields roughly 100–120 board feet and might cost $30–$60 to mill, plus a travel fee of $50–$150 depending on distance.

Q: How accurate is the board foot estimate for my log?

The Doyle rule is a planning estimate. Expect real yield within 10–25% of the calculator's output depending on log taper, sweep, and defects. A straight, defect-free log will be closest to the estimate; a curved or knotty log will yield less.

Wondering how much usable lumber is in your log — and what it might cost to have it milled? Enter your log’s dimensions below for an estimate before you call a sawyer. This is a planning tool; actual yield depends on taper, defects, the sawyer’s setup, and how you want it cut.

Small-end diameter (inches) Measured inside the bark, at the narrow end

Log length (feet) Usable straight length

Number of logs

Estimated board feet (Doyle rule) —

Scribner rule (comparison) —

Est. milling cost — by board foot ($0.25–$0.50/bf) —

Est. milling cost — hourly ($60–$125/hr)* —

*Hourly estimate assumes roughly 200–250 board feet sawn per hour, typical for a portable band mill on clean logs. Add travel/setup fees and possible blade charges for metal in yard trees. Ranges are planning estimates, not quotes.

Which rule should I use? Most small portable sawyers estimate with the Doyle rule, so that’s the headline number here. Doyle under-estimates small logs and over-estimates large ones; the Scribner figure is shown for comparison. Your actual usable yield often lands between the two.

How to calculate board feet from a log

The Doyle log rule is the most widely used formula among portable sawyers in the eastern and central US. It estimates the board feet of usable lumber from a log’s small-end diameter (D, in inches) and length (L, in feet):

Doyle formula: ((D − 4) ÷ 4)² × L

For example, a 16-inch diameter log that is 12 feet long yields: ((16 − 4) ÷ 4)² × 12 = 9² × 12 = 108 board feet by the Doyle rule.

The Scribner rule is diagram-based and common in the West. It generally gives a higher count for small-diameter logs. For the same 16-inch, 12-foot log, Scribner yields roughly 128 board feet — about 18% more.

Quick-reference table: common log sizes

Diameter (in)	Length (ft)	Doyle (bf)	Scribner (bf)	Est. milling cost
8"	8	16	24	$4 – $12
10"	8	18 bf	30 bf	$6 – $15
12"	10	40 bf	56 bf	$12 – $28
16"	12	108 bf	128 bf	$30 – $64
20"	14	224 bf	240 bf	$56 – $120
24"	16	400 bf	410 bf	$100 – $205

Cost estimates use $0.25–$0.50 per board foot, averaged between Doyle and Scribner. Actual quotes vary by region, travel, and log condition.

What affects your real yield

Taper and sweep: a curved or heavily tapered log yields less than a straight one of the same diameter.
Defects: rot, knots, cracks, and embedded metal (nails, fencing) reduce usable lumber and can damage the saw blade.
Cut pattern: thick slabs vs. dimensional boards change both the count and the waste.
Kerf: every cut turns some wood into sawdust — thin-kerf band mills waste less than circular mills.
Species: density doesn’t change the board foot count, but it affects milling time and blade wear, which some sawyers price accordingly.

Frequently asked questions

How do I calculate board feet from a log?

Measure the small-end diameter (in inches, inside the bark) and the usable log length (in feet). Plug into the Doyle formula: ((diameter − 4) ÷ 4)² × length. Or use the calculator above — it calculates both Doyle and Scribner instantly and estimates your milling cost range.

What is a board foot and how is it different from a linear foot?

A board foot is a unit of lumber volume equal to a piece 12 inches wide, 12 inches long, and 1 inch thick (144 cubic inches). A linear foot is simply length — no width or thickness. Sawyers and lumber yards use board feet because it accounts for all three dimensions and gives a consistent basis for pricing regardless of how the log is cut.

What’s the difference between the Doyle rule and the Scribner rule?

Both estimate board feet from a log, but they use different formulas and were developed for different regions. The Doyle rule is dominant east of the Rockies and among portable sawyers nationwide; it tends to under-count small logs (under 14 inches) and slightly over-count large ones. The Scribner rule is more common in the Pacific Northwest and gives a higher estimate for small logs. For most portable sawmill quotes, ask which rule your sawyer uses — the difference on a single log can be 15–30%.

How much does it cost to mill a log into lumber?

Most portable sawyers charge either by the board foot ($0.25–$0.50/bf) or by the hour ($60–$125/hr). A typical yard tree — say a 16-inch oak, 12 feet of usable log — yields roughly 100–120 board feet and might cost $30–$60 to mill, plus a travel fee of $50–$150 depending on distance. The calculator above gives you a range before you call. See our full cost guide for more detail.

How accurate is the board foot estimate for my log?

The Doyle rule is a planning estimate, not a precise measurement. Expect real yield to land within 10–25% of the calculator’s output depending on log taper, sweep, and defects. A perfectly straight, defect-free log will be closer to the estimate; a curved or knotty log will yield less. Your sawyer may adjust the scale on-site after inspecting the log.

What size log do I need for a specific lumber project?

Work backward from the board feet you need. For a dining table top (roughly 40–60 bf of slabs), a single straight 18–20 inch log 8–10 feet long is usually enough. For a timber-frame outbuilding (500–1,000 bf), plan on 5–10 good-sized logs. Use the calculator to check your specific logs before scheduling a sawyer.

Can I use this calculator for standing trees?

Not directly — standing tree yield requires estimating merchantable height and accounting for taper, which the Doyle formula doesn’t handle well. A rough approach: estimate the number of 8–16 foot logs you can get from the tree, measure or estimate the diameter at 4.5 feet (breast height), subtract 2–4 inches for taper on upper logs, then run each log section through the calculator and add the results.

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