Log Scale Doyle Calculator
Doyle board feet from log dimensions.
What it does
Sawlogs sell by scale before the mill runs. Doyle estimates board feet from small end diameter and length with one line: diameter minus four, squared, times length over sixteen. A twenty inch by sixteen foot log scales 256 board feet gross.
The tool above runs Doyle both ways. Defaults give 256 board feet with 0.604 cubic meters. A fifty centimeter by four meter log gives 202 board feet. Twelve inches by eight feet gives only 32, showing how harsh Doyle runs on small timber.
Scale is gross by design. Sweep, rot, taper, slabs, and kerf all deduct after, and buyers name the scale in the contract. International quarter inch treats small logs more kindly, so confirm which rule prices the pile.
This page scales sound cylinders only. It does not grade defects, pick rules, or settle payments. Walk the pile with the buyer scale first.
How to use
- Pick imperial (in, ft) or metric (cm, m).
- Enter the small end diameter.
- Enter the log length.
- Read board feet first.
- Read cubic meters beside.
- Apply defect deductions after.
Formula
- D
- Small end diameter inside bark, in inches.
- L
- Log length in feet.
- BF
- Lumber tally before deductions.
Gross Doyle scale on small end diameter inside bark. At 4 in and below the rule gives zero or less, floored at zero. Defect deductions and buyer rules sit outside this line.
Worked example
Example: 20 in by 16 ft log
Defaults: imperial 20 in diameter by 16 ft long, small end scale. Slabs and kerf excluded.
- Inputs (imperial default): 20 in small end by 16 ft.
- Math: (20 minus 4) squared times 16 / 16.
- Board feet: 256 squared over 1 is 256 board feet.
- Metric: 0.604 m3.
- A 50 cm by 4 m log gives 202. Tool shows the same.
Reference table
| Log | Board feet | Cubic m |
|---|---|---|
| 20 in by 16 ft | 256 board feet | 0.604 m3 |
| 50 cm by 4 m | 202 board feet | 0.476 m3 |
| 12 in by 8 ft | 32 board feet | 0.076 m3 |
| 16 in by 12 ft | 108 board feet | 0.255 m3 |
| 30 cm by 3 m | 38 board feet | 0.089 m3 |
Limits
- Gross scale. Defects excluded.
- Doyle rule only. Buyers vary.
- Small logs undervalued. Know the bias.
- Cylinder assumed. Flare ignored.
Common mistakes
- Scaling big end instead of small.
- Forgetting inside bark measure.
- Pricing without naming the rule.
- Skipping defect deductions.
- Mixing Doyle with International quotes.
Try it yourself
Quick checks. Answers sit tucked under each question.
50 cm by 4 m?
Inches 19.69 with 13.12 ft give (15.69 squared times 13.12 / 16) 202 board feet with 0.476 m3.
12 in by 8 ft?
(12 minus 4) squared times 8 / 16 is 32 board feet.
Questions
What is the Doyle formula?
(D minus 4) squared times L / 16. Here 256 board feet.
Which diameter?
Small end inside bark. Taper and sweep need deductions after.
How are cubic meters figured?
Board feet times 0.00236. Here 0.604 m3.
Is Doyle fair on small logs?
Yes for small logs. Doyle under scales below about 28 in; use International for small timber.
Does this grade defects?
No. Sweep, rot, and taper deductions come after the gross scale.
Is Doyle universal?
No. Mill tally rules vary. Confirm the buyer scale first.