Board Foot Calculator for Lumber: What Is a Board Foot?
A board foot is a volume unit — 12 inches × 12 inches × 1 inch. Once you understand that, pricing lumber and estimating projects gets a lot simpler.
What Is a Board Foot?
A board foot (BF or FBM) is a unit of lumber volume equal to 144 cubic inches — the equivalent of a piece 12 inches wide, 12 inches long, and 1 inch thick.
Board feet are the standard unit for pricing hardwood lumber. Softwood (framing lumber) is typically sold by the linear foot or piece, but hardwood — oak, walnut, maple — is priced per board foot.
One board foot of 4/4 (one-inch thick) oak measures 12×12 inches. The same volume in 8/4 (two-inch) stock is 6×12 inches. Thickness in hardwood is described in quarters of an inch.
The Board Foot Formula
Board feet = (thickness in inches × width in inches × length in inches) ÷ 144. Or if length is in feet: (thickness × width × length in feet) ÷ 12.
Example: a board 1 inch thick, 8 inches wide, and 10 feet long = (1 × 8 × 10) ÷ 12 = 6.67 board feet.
A 2-inch thick board 6 inches wide and 8 feet long = (2 × 6 × 8) ÷ 12 = 8 board feet. The formula is the same regardless of dimensions — just plug in and divide.
Free tool: Board Foot Calculator →
Rough vs. Surfaced Lumber
Hardwood is sold rough (rough-sawn, as it came off the mill) or surfaced (planed to a smooth face). Rough lumber is measured at its rough thickness; surfaced lumber is measured at its rough thickness even though the planed thickness is smaller.
A 4/4 board is one inch rough. After surfacing to S2S (surfaced two sides), it typically measures 13/16 inch. You pay for the rough dimension, not the finished one.
Always calculate board feet using the rough dimensions listed on the tag or invoice. Using the finished dimensions will undercount your material and undercharge for your project.
Using Board Feet to Estimate a Project
For a table, cabinet, or wood project, list every part with its rough dimensions, calculate board feet for each, add them up, and add 20% for waste (rough lumber has defects you'll cut around).
A simple dining table top that's 36×84 inches at 1.5 inches finished (call it 2-inch rough stock): 2 × 36 × 84 ÷ 144 = 42 board feet rough. Add 20% waste: order 51 board feet.
Our board foot calculator lets you enter multiple pieces and get a total instantly — useful when pricing a project or comparing quotes from different lumber yards.
Board Foot Pricing
Common hardwood prices per board foot: poplar $3–5, red oak $5–8, hard maple $6–9, cherry $8–12, walnut $10–16. Figured or specialty woods go much higher.
Price per board foot varies by grade. Select and Better (S&B) is the clearest, most expensive grade. #1 Common has more knots and character; #2 Common has significant defects. For furniture, S&B or #1 Common is typical.
Buy slightly more than you need. Running short on a species means a second order, and the new boards may not match the grain or color of the first batch. For matched-grain projects, buy all your lumber from the same slab.
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FAQ
- What is a board foot of lumber?
- A board foot is a volume unit equal to 144 cubic inches — the same as a piece 12 inches wide, 12 inches long, and 1 inch thick. It's the standard unit for pricing hardwood lumber.
- How do I calculate board feet?
- Use this formula: (thickness in inches × width in inches × length in feet) ÷ 12. For example, a 1×6×10-foot board = (1 × 6 × 10) ÷ 12 = 5 board feet.
- Why is hardwood sold by board feet but framing lumber is not?
- Hardwood comes in random widths and lengths, so board feet is the only consistent way to measure volume. Framing lumber is standardized in dimensions and lengths, so linear feet and piece counts work fine.
- How many board feet are in a 2x4x8?
- A 2×4×8 stud = (2 × 4 × 8) ÷ 12 = 5.33 board feet. Note: the actual dimensions of a 2×4 are 1.5×3.5 inches, but lumber is calculated using the nominal dimensions.