Board feet calculator for lumber and logs
The short answer
Board feet in lumber = nominal thickness in inches x nominal width in inches x length in feet, divided by 12, so a 2x4 that is 8 feet long holds 5.33 board feet. For a log, measure the small end inside the bark and the length, then pick a log rule.
Board feet calculator
Use this board feet calculator to add up a lumber pile or scale a log by the three common log rules.
Your numbers
Your answer
200 board feet
20 pieces of 2 x 6 lumber, 10 feet long, come to 200 board feet.
- All pieces200
- Each piece10
Each piece is 10 board feet.
At a glance
- One board foot
- 1 x 12 inches, 1 foot long
- A 2x4, 8 feet long
- 5.33 board feet
- Log rules in use
- Scribner, Doyle, International
- Measure a log at
- The small end, inside the bark
How the board feet calculator works
For lumber, it follows the American Softwood Lumber Standard:
- Take the nominal thickness in inches (a 2x6 is 2) and the nominal width in inches (6).
- Turn the width into feet by dividing by 12.
- Multiply thickness x width in feet x length in feet. That is the board feet in one piece.
- Multiply by the number of pieces.
For logs, it runs three log rules from Purdue Extension's scaling guide. D is the diameter across the small end, inside the bark, in inches. L is the length in feet.
- Doyle: (D - 4) x (D - 4) x L / 16. The 4 inches allow for slabs and edgings.
- Scribner: (0.79 x D x D - 2 x D - 4) x L / 16, rounded to the nearest 10 board feet.
- International 1/4-inch: Grosenbaugh's formula, which allows for the log getting wider along its length, rounded to the nearest 5 board feet.
What it assumes
- Lumber is counted by its nominal size, the way it is sold, not its planed size.
- Logs are straight and sound. A real scaler takes off for rot, crook and other defects.
- The Scribner number comes from a formula. Mills that use the Scribner Decimal C table can get a slightly different figure.
- No prices. This tool measures wood; it does not value it.
Board feet for common lumber sizes
| Size | Length | Board feet |
|---|---|---|
| 1x6 | 8 ft | 4 |
| 1x12 | 10 ft | 10 |
| 2x4 | 8 ft | 5.33 |
| 2x4 | 10 ft | 6.67 |
| 2x6 | 8 ft | 8 |
| 2x6 | 12 ft | 12 |
| 2x8 | 16 ft | 21.33 |
| 2x10 | 10 ft | 16.67 |
| 2x12 | 12 ft | 24 |
| 4x4 | 8 ft | 10.67 |
| 6x6 | 10 ft | 30 |
A Bonners Ferry example
Say you are building a woodshed outside Bonners Ferry and need 20 pieces of 2x6, each 10 feet long. 2 x (6 / 12) x 10 = 10 board feet a piece, and 10 x 20 = 200 board feet.
Now say you have a straight 16-foot log, 16 inches across the small end inside the bark.
- Doyle: (16 - 4) x (16 - 4) x 16 / 16 = 144 board feet.
- Scribner: (0.79 x 16 x 16 - 2 x 16 - 4) x 16 / 16 = 166.24, so 170 board feet.
- International 1/4-inch: about 180.5, so 180 board feet.
Which log rule to use
There is no single right rule. Purdue Extension says local tradition usually decides which rule is used to buy and sell logs. The rules are fair as long as everyone uses the same one.
So around Bonners Ferry, expect a mill or log buyer to talk in Scribner board feet or in cubic feet.
Facts this tool uses
| Fact | Figure | Source |
|---|---|---|
| Board feet in lumber | Nominal thickness in inches x nominal width in feet x length in feet | NIST, American Softwood Lumber Standard PS 20-10Section 2.2, Board measure, checked Oct 28, 2026 |
| Doyle rule | (D - 4)² x L / 16 | Purdue Extension FNR-191, Log and Tree Scaling TechniquesDoyle formula checked Oct 28, 2026 |
| Scribner rule (formula) | (0.79 D² - 2 D - 4) x L / 16 (Bruce and Schumacher, 1950) | Purdue Extension FNR-191, Log and Tree Scaling TechniquesScribner formula checked Oct 28, 2026 |
| International 1/4-inch rule | Grosenbaugh's formula; values rounded to the nearest 5 board feet | Purdue Extension FNR-191, Log and Tree Scaling TechniquesInternational rule formulas checked Oct 28, 2026 |
| D and L in the log rules | D = diameter inside the bark at the small end, inches; L = log length, feet | Purdue Extension FNR-191, Log and Tree Scaling TechniquesVariable definitions checked Oct 28, 2026 |
| Commercial log scaling in Idaho | By Scribner decimal "C" or by cubic volume; other methods only as the Board decides on written request. One decimal "C" equals 10 board feet | Idaho Board of Scaling Practices, IDAPA 20.06.01Section 500 and the decimal C definition checked Oct 28, 2026 |
| Where each rule is used | Doyle: most used, especially on private timber in the East and South. Scribner: widely used by the Forest Service in the western United States | Purdue Extension FNR-191, Log and Tree Scaling TechniquesRule history checked Oct 28, 2026 |
Next step
Have logs to mill or a stand to cut? Logging and timber businesses in Bonners Ferry