How Board Feet Is Measured in Lumber (A Simple Guide)

Dec 4

Whether you're buying rough-cut lumber, planning a project, or reviewing a sawmill invoice, the term “board feet” comes up constantly. But most people don’t fully understand what a board foot actually measures.

At Grabeldinger Firewood & Logging LLC, we scale board feet day in and day out, and below is the clear, consistent method we rely on.

What Is a Board Foot?

A board foot (BF) is a unit of volume used for measuring lumber. One board foot equals:

1 inch thick × 12 inches wide × 12 inches long
—or—
144 cubic inches of wood

Board feet measure volume — not linear length. That’s why a thicker or wider board adds up quickly, even if the length is the same.

The Standard Board Foot Formula

This is the formula used by mills, lumberyards, and sawyers for both rough-cut and dimensional lumber:

Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12

Examples:

2×4×8’ → (2 × 4 × 8) ÷ 12 = 5.33 BF
1×6×10’ → (1 × 6 × 10) ÷ 12 = 5 BF
2×8×12’ → (2 × 8 × 12) ÷ 12 = 16 BF

This applies to rough-sawn boards, dimensional lumber, timbers, decking, framing, and most standard boards.

Understanding 4/4, 5/4, 8/4 Lumber Thickness

In rough-cut lumber, thickness is often listed in “quarters”:

4/4 = 1 inch
5/4 = 1.25 inches
6/4 = 1.5 inches
8/4 = 2 inches
12/4 = 3 inches

These are measured before planing. Even once planed smooth (S3S or S4S), board feet are still calculated from the rough-sawn dimension.

For more detail on quarters, planed thickness, and wood grades, you can link to our related article:
Lumber Buying Basics: Understanding 4/4, Board Feet, and Wood Grades.

Quick Board Foot Reference Chart

  
    Size
    Length
    Board Feet
  
    1x6
    8'
    4 BF
  
    2x6
    8'
    8 BF
  
    2x8
    12'
    16 BF
  
    2x10
    12'
    20 BF
  
    3x12
    12'
    36 BF

Do Logs Use the Same Board-Foot Formula?

No — logs are measured differently.
The formula above applies only to lumber that has already been milled.

Logs are scaled using rules like Doyle, Scribner, and International ¼", which estimate usable lumber after saw kerf, taper, and waste. If you'd like to learn how we scale standing timber and logs, visit:

How We Scale Logs: Doyle vs. International (Central NY)
https://www.grabeldingerfirewood.com/woodlot-wisdom/how-we-scale-logs-doyle-vs-international-central-ny

Why Understanding Board Feet Helps Buyers

Knowing board-foot measurement allows you to:

Compare lumber prices accurately
Estimate material needs for a project
Understand sawmill or lumberyard invoices
Avoid over- or under-ordering
Choose between 4/4, 5/4, 8/4, etc., with confidence

And when you buy rough-cut from us, every invoice clearly breaks out species, thickness, width, length, board footage, and price per BF. No guesswork — just clear, honest lumber math.

Final Thoughts

Board feet give builders, hobbyists, and woodlot owners a simple, universal way to measure lumber volume. With a single formula, you can plan your project, compare pricing, and better understand what you're actually getting.

If you ever need help calculating board footage or want custom lumber milled for your next job, we’re here to help.

Ken Grabeldinger https://www.grabeldingerfirewood.com