What is a Board Foot?
A board foot (BF) is the standard unit of measurement for hardwood lumber in North America. One board foot equals a volume of 144 cubic inches, equivalent to a piece that is 1 inch thick, 12 inches wide, and 12 inches long (1 foot). Lumber dealers price hardwood by the board foot, making this calculation essential for accurate cost estimation.
Unlike dimensional softwood lumber (2x4s, 2x6s, etc.) which is sold by the linear foot, hardwoods like oak, maple, walnut, and cherry are sold by the board foot because they come in random widths and lengths. Understanding board feet helps you compare prices and estimate project costs accurately.
Board Foot Formula
Alternatively:
Quarter System
Hardwood thickness is traditionally described in quarters of an inch:
| Quarter | Rough Thickness | Surfaced (S2S) |
|---|---|---|
| 4/4 (four-quarter) | 1" | 3/4" (13/16") |
| 5/4 | 1-1/4" | 1-1/16" |
| 6/4 | 1-1/2" | 1-5/16" |
| 8/4 | 2" | 1-3/4" |
| 12/4 | 3" | 2-3/4" |
| 16/4 | 4" | 3-3/4" |
Lumber Pricing
- Board foot prices vary widely by species: common pine $2-4/BF, oak $4-8/BF, walnut $8-15/BF, exotic species $10-30+/BF.
- Rough (unsurfaced) lumber costs less than surfaced (S2S or S4S).
- FAS (First and Seconds) grade commands premium prices over #1 Common or #2 Common.
- Kiln-dried lumber costs more than air-dried or green lumber.
Frequently Asked Questions
How many board feet are in a 1x6x8?
A 1" thick x 6" wide x 8' long board contains (1 x 6 x 8) / 12 = 4 board feet. If priced at $5/BF, this board would cost $20.
Do I use rough or finished dimensions?
Lumber dealers price based on the rough (nominal) thickness before surfacing. A board sold as 4/4 is priced at 1 inch thick, even though it may only be 3/4" after surfacing. Width and length are typically actual measurements.
How do I account for waste?
For woodworking projects, add 20-30% to your board foot calculation for waste from cutting, defects, and milling. For simple projects with long straight pieces, 15% may be sufficient. Complex projects with many small parts may need 30-40% extra.