🪵 Board Feet in a Log Calculator
Estimate log scale with Doyle, Scribner Decimal C, International 1/4, or cubic volume, then adjust for taper, species, moisture, defect, kerf loss, and usable slabs.
📌 Log And Species Presets
Load a real saw-log scenario, then tune the small-end diameter, length, log rule, taper, defect, kerf loss, slab recovery, species, and moisture content.
⚙ Log Scale Inputs
🧮 Log Rule And Species Comparison Grid
These cards update from the same diameter, length, taper, and species, so you can see how the selected log rule compares with alternate scaling methods.
🌲 Species Recovery Grid
📚 Log Rule Reference Tables
| Log Rule | Core Formula Basis | Where It Helps | Planning Note |
|---|---|---|---|
| Doyle | ((D - 4)² x L) / 16 | Large hardwood logs | Can underrun small-diameter logs sharply |
| Scribner Decimal C | (0.79D² - 2D - 4) x L / 16 | General saw-log scaling | Middle estimate for many small mills |
| International 1/4 | (0.22D² - 0.71D) x L / 4 | Mixed diameters and grade logs | Often closer to actual sawmill recovery |
| Cubic estimate | Frustum volume x 12 bf per ft³ | Taper and large-end comparison | Gross fiber basis before sawing limits |
| Species | Density at 12% | Recovery Factor | Typical Note |
|---|---|---|---|
| Eastern white pine | 25 lb/ft³ | 1.04 | Light, easy sawing, modest defect |
| Douglas fir | 33 lb/ft³ | 1.02 | Strong structural stock, predictable yield |
| Red oak | 44 lb/ft³ | 0.98 | Dense hardwood, checks and sweep matter |
| Hard maple | 44 lb/ft³ | 0.96 | Hard cutting, defect deductions matter |
| Diameter Class | Doyle Tendency | Scribner Tendency | International Tendency |
|---|---|---|---|
| 8 to 11 in | Very conservative | Conservative | Better small-log yield |
| 12 to 15 in | Low to moderate | Practical mill scale | Often close to recovery |
| 16 to 23 in | Useful hardwood scale | Common saw-log scale | Stable comparison rule |
| 24 in and up | Less conservative | Strong estimate | Useful for high recovery logs |
| Sawing Variable | Low Loss | Typical Loss | High Loss |
|---|---|---|---|
| Bandmill kerf | 6% to 9% | 9% to 13% | 14% to 18% |
| Circular mill kerf | 10% to 14% | 14% to 20% | 20% to 28% |
| Defect deduction | 0% to 5% | 6% to 15% | 16% to 35% |
| Saved slabs | 1 to 3 bf each | 3 to 8 bf each | Only if sound |
💡 Practical Log Scale Tips
The amount of usable lumber within a log is a complex calculation due to various factors that play a role in the measurement. Factors to consider in calculating the amount of usable lumber within a log include the diameters of the log, the length of the log, the taper of the log, the species of the wood within the log, and the amount of rot within the log. The amount of usable lumber within a log as seen by an individual may differ from the amount that a sawmill will pay for the log.
The sawmill use a log scaling rule to determine the amount of lumber within the log, and each log scaling rule utilizes slightly different assumption about the wood within the log. Some of the more common log scaling rules include the Doyle rule, the Scribner rule, and the International 1/4 rule. Each rule utilizes a calculator to determine how much lumber is within each log that enters the sawmill.
How to Measure Usable Lumber in a Log
Additionally, sawmills use these calculators to determine if changing the log scaling rule will change the price of the lumber that is being sold. Another factor that a sawmill measures prior to estimating the amount of lumber within a log is the taper of the log. A person measures the taper of a log by seeing how the diameter of the log changes from one end of the log to the other end of the log.
While many logs appear to have a consistent diameter, some logs may contain a taper that allows the diameter of the log to increase by an inch or more over a distance of sixteen feet. Such an increase in the diameter of the log indicates that there will be more lumber within the large end of the log than within the small end of the log. The lumber mill’s log calculator accounts for this taper within its calculation, especially when building an estimate of the volume of logs that will be used for veneer or saw logs.
In addition to the taper of the log, the presence of defect within the log, and by the kerf of the saw blade, affects the usable lumber within a log. While the sawmill worker will subtract the amount of lumber that is lost to defects within the log, the saw blade will remove some of the lumber within the log as well. Such wood that is lost to the saw blade is known as the kerf.
The lumber log calculator accounts for both the loss of lumber due to defects within the log and the loss of lumber due to the saw blade kerf. Furthermore, the sawmill may use different sawing pattern within the log. Some sawing patterns may create more waste within the sawmill than others.
The species of the wood within the log will impact the volume and the weight of the lumber that is produced from that log. Some wood species are denser than others, which means that a higher number of board-feet of a species of wood will have a higher weight than a lower number of board-feet of a less dense type of wood. Additionally, some wood species will shrink more than other wood species as they dry.
The recovery factor within the calculator accounts for each of these species differences in relation to the lumber that can be produced from that specific species of wood. The moisture content of the log will also impact the weight of the lumber and the volume of the log. A log that contains a higher amount of moisture than a dry log will lose some of that moisture, which will result in the loss of some of the weight of the log.
Additionally, as the log loses moisture, it will also lose some of its volume. To account for this loss of volume within the log due to moisture loss, a lumber log calculator will include an allowance for shrinkage based off the species of the wood within the log. The primary use of a log scaling exercise is for the purpose of comparison.
The sawmill may use the log scaling rules and the log calculator to compare the impact that each variable within the log has upon the amount of usable lumber within that log. The sawmill may also use the calculator to compare the impact that each different defect call has upon the usable lumber within the log. The sawmill will use the calculator to make decisions about lumber production when the inputs into the calculator are set to realistic variables.
