A 20-inch log that is 10 feet long holds about 160 board feet of lumber by the Doyle log rule. A 14-inch log of the same length holds about 63. The chart below covers logs from 12 to 30 inches across at 8, 10 and 12 feet long.
Measure the small end of your log, find the row, and read across to your length. That number is a fair starting point for how much lumber you'll get and what milling might cost.
Board-foot chart (Doyle rule)
Small-end diameter is measured inside the bark. Numbers are rounded to the nearest board foot.
| Small-end diameter | 8 ft log | 10 ft log | 12 ft log |
|---|---|---|---|
| 12 in | 32 | 40 | 48 |
| 14 in | 50 | 63 | 75 |
| 16 in | 72 | 90 | 108 |
| 18 in | 98 | 123 | 147 |
| 20 in | 128 | 160 | 192 |
| 22 in | 162 | 203 | 243 |
| 24 in | 200 | 250 | 300 |
| 26 in | 242 | 303 | 363 |
| 28 in | 288 | 360 | 432 |
| 30 in | 338 | 423 | 507 |
The formula behind every number: board feet = (D − 4)² × L ÷ 16, where D is the small-end diameter in inches and L is the log length in feet.
Worked example: a 20-inch log, 10 feet long. 20 minus 4 is 16. 16 squared is 256. 256 times 10 is 2,560. Divide by 16 and you get 160 board feet.
What a board foot is
A board foot is a piece of wood 12 inches long, 12 inches wide and 1 inch thick. That's 144 cubic inches. Lumber is bought, sold and milled by this unit, so it's worth knowing how to figure it.
For a board, multiply thickness in inches by width in inches by length in feet, then divide by 12:
- A 1-inch by 6-inch board, 8 feet long: 1 × 6 × 8 ÷ 12 = 4 board feet.
- A 2-inch by 10-inch plank, 12 feet long: 2 × 10 × 12 ÷ 12 = 20 board feet.
- A 2-inch walnut board, 8 inches wide and 6 feet long: 2 × 8 × 6 ÷ 12 = 8 board feet.
A log rule does the same job before the log is sawn. It predicts how many board feet will come out of a round log once the bark, the outside slabs and the saw kerf are gone.
How to measure your log
You need a tape measure and a few minutes.
- Find the small end. Logs taper. The small end limits how wide the boards can be, so that's the end log rules use.
- Measure across the small end, inside the bark. Don't include bark thickness. If the end isn't round, measure the widest and narrowest directions and average them.
- Measure the length in feet. Round down to the whole foot. If you have 10 feet 5 inches, count it as 10 feet. The extra inches are trim allowance, and the boards get squared up to the even length.
- Check for trouble. Note any rot in the ends, a hollow center, big knots, a sweep or crook, or signs of nails and wire. These all reduce what you get.
For a whole tree, measure each log separately and add them up. Say the butt log is 20 inches at the small end and 10 feet long (160 board feet), and the next log up is 16 inches and 8 feet (72 board feet). The tree scales about 232 board feet by Doyle.
Send us those measurements with a few photos and we can give you a much better read than any chart. A photo of each end tells us a lot.
Why Doyle shorts small logs
The Doyle rule is old and simple. MU Extension names Doyle and International 1/4-inch as the two most commonly used log rules in Missouri (MU Extension G5050, How to Measure Trees and Logs). Doyle also has a known bias: it underestimates small logs and gets closer to real yield as logs get bigger.
The reason is the "minus 4" in the formula. Doyle subtracts 4 inches from the diameter to account for slabs and bark, no matter how big the log is. On a 30-inch log, losing 4 inches is minor. On a 12-inch log, it's a third of the diameter, and the formula throws away more wood than a mill actually loses.
So if your log is in the 12- to 16-inch range, expect the actual lumber to come out above the chart number. That gap is called overrun. On big logs, the chart and the actual pile get closer together.
What that means for you:
- If you're paying for milling by the board foot, the rule your mill uses changes the bill. Ask which one.
- If you're selling small logs, a Doyle scale will come in lower than what the log actually saws out.
- If you're estimating lumber for a project, treat the Doyle number as a floor for small logs, not a promise.
Other log rules: Scribner and International 1/4-inch
Two other log rules are common in the U.S. International 1/4-inch is the other rule you'll most often see in Missouri.
- Scribner is built from diagrams of boards drawn inside circles of different sizes. It's used widely in the western U.S. and by some buyers elsewhere. It also tends to come in low on small logs, though usually less so than Doyle.
- International 1/4-inch is built from a formula that accounts for a 1/4-inch saw kerf and the taper of the log. It's generally considered the closest of the three to what a mill actually saws out; MU Extension calls it probably the most accurate.
All three give similar numbers on large logs and different numbers on small ones. We don't reprint their tables here because the same log can scale noticeably different under each, and a chart without the rule's name on it causes more confusion than it solves.
Why your lumber pile won't match the chart exactly
A log rule is an estimate made on the outside of the log. What comes out depends on what's inside and how it's cut.
- Sweep and crook. A curved log loses boards on the outside of the bend. Short, straight logs often beat long, crooked ones.
- Rot, hollows and ring shake. A hollow center or punky heartwood can cut yield sharply. The ends usually show it.
- Metal. Nails, wire and fence staples mean we cut around damaged wood. Yard trees carry the most. See why yard trees cost more to mill.
- Cut pattern. Wide live-edge slabs keep more wood than squared boards. Quartersawing takes more passes and gives up some yield in exchange for stability and figure. See flat-sawn, quarter-sawn and live-sawn oak.
- Thickness. Each pass of the saw turns a strip of wood into sawdust. More, thinner boards means more kerf loss than fewer, thicker ones.
How big a log we can take
For help deciding whether a log is worth the trip at all, read is my tree worth milling?, and see custom sawmilling for how a milling job works from photos to pickup.
From board feet to a price
Once you have a board-foot number, you can rough out cost. Our pricing page shows national milling ranges and a milling cost estimator that uses this same Doyle formula. For reference, custom milling nationally runs about $0.35 to $0.75 per board foot (national range, not our price), and small or crooked logs cost more per foot.
Get a Quote
Measure the small end and the length, take a photo of each end and one of the whole log, and send them to us. We'll tell you about how much lumber is in it and what milling it would cost.