Board Foot Calculator
Board feet and lumber cost.
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Board feet are how lumber is measured and priced in the US and Canada. Enter a board's thickness, width, and length and this calculator gives the board feet — for a single piece or a whole batch — and the total cost at your price per board foot.
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Board Feet — The Quick Answer
One board foot is 144 cubic inches — the volume of a 1 in × 12 in × 12 in board. Calculate it as (thickness × width × length in inches) ÷ 12. A 2×6 measuring 8 ft is 8 board feet.
Shortcut
Board feet = (thickness × width × length) ÷ 12
Common boards and their board feet
| Size | Length | Board feet |
|---|---|---|
| 1 × 4 | 8 ft | 2.67 |
| 1 × 6 | 8 ft | 4.0 |
| 2 × 4 | 8 ft | 5.33 |
| 2 × 6 | 8 ft | 8.0 |
| 2 × 8 | 8 ft | 10.67 |
| 2 × 10 | 8 ft | 13.33 |
| 4 × 4 | 8 ft | 10.67 |
Board feet use nominal dimensions — the labelled size, not the actual finished size. A '2×4' is measured as 2 in × 4 in for pricing even though it's really about 1.5 in × 3.5 in.
How It Works
The Formula
Volume in board feet
Formula
Board feet = (T × W × L) / 12 (measure T, W, L in inches)
Variables
Thickness (inches)
Nominal thickness — the first number in a board's size (the '2' in 2×4).
Width (inches)
Nominal width — the second number in a board's size (the '4' in 2×4).
Length (inches)
Length in inches. Divide the product by 12 to convert to board feet; each board foot is 144 cubic inches.
Note: The divisor is 12 when length is in inches (since 1 board foot = 1 in × 12 in × 12 in = 144 in³, and 144 ÷ 12 = 12). If you measure length in feet, the formula becomes (T × W × L in feet) ÷ 12.
Worked Example: A 2 × 6 Board, 8 Feet Long
Board feet from inches
Measure thickness, width, length in inches
2 in × 6 in × 96 in (8 ft)
Multiply them together
2 × 6 × 96 = 1,152
Divide by 144
1,152 ÷ 144 = 8 board feet
Multiply by quantity and price
× number of boards, × price per board foot for cost
Reference Guide
| Size | Length | Board feet |
|---|---|---|
| 1 × 4 | 8 ft | 2.67 |
| 1 × 6 | 8 ft | 4.0 |
| 2 × 4 | 8 ft | 5.33 |
| 2 × 6 | 8 ft | 8.0 |
| 2 × 8 | 8 ft | 10.67 |
Reading the Result Correctly
Nominal sizes, and board feet vs linear feet
One board foot is 144 cubic inches — a 1 in × 12 in × 12 in board. It fairly prices lumber of different thicknesses and widths by actual material, which is why hardwood is sold this way rather than by length.
Best for: Understanding how hardwood is priced
A '2 × 4' is a nominal label — the rough size before drying and planing. The finished board is about 1.5 × 3.5 in. Board-foot pricing uses the nominal dimensions, but build to the actual, smaller sizes.
Best for: Avoiding 'why isn't my 2×4 actually 2×4?' surprises
Real projects need extra for defects you cut around, mistakes, and offcuts. For furniture-grade work, 15–20% extra is a sensible allowance; rough construction can get away with less.
Best for: Ordering enough lumber for the job
What Is a Board Foot?
A board foot is a unit of lumber volume equal to 144 cubic inches — the volume of a board one inch thick, twelve inches wide, and twelve inches long. It's how hardwood and rough lumber are sold in the US and Canada, because it prices wood of different thicknesses and widths by actual material rather than just length. Calculate it as thickness × width × length in inches, divided by 144 (or divide by 12 when length is in feet). One quirk worth knowing: board-foot pricing uses nominal sizes — a '2 × 4' is counted as 2 × 4 even though its finished size is about 1.5 × 3.5 in. This calculator handles single boards or a batch and can estimate cost.
Key Features
💡 Pro Tips
- →Order by nominal size but design and cut to the actual, smaller finished dimensions.
- →Add 15–20% for furniture-grade work to cover defects and offcuts; less for rough framing.
- →For hardwood, inspect for knots and splits — you pay by volume, so wood you'll cut away is wasted money.
- →Linear feet (length only) and board feet (volume) are different units; confirm which a supplier is quoting.
Common Mistakes
Confusing board feet with linear feet
Linear feet ignore width and thickness; board feet measure volume. A thick, wide board has far more board feet than a thin one of the same length, so the two prices aren't comparable.
Building to nominal dimensions
A '2 × 8' is really about 1.5 × 7.25 in finished. Designing as if it's a full 8 inches wide leaves joints and fits wrong.
Ordering no extra
Defects, mistakes, and offcuts mean you need more than the exact board feet. Skipping a 15–20% allowance on fine work usually means a second trip.
Research & Citations
Sources and standards referenced for the factual claims on this page
- [1]
USDA Forest Products Laboratory (2021). Wood Handbook — Wood as an Engineering Material. USDA FPL.
Reference on lumber measurement and properties.
View source - [2]
National Hardwood Lumber Association (NHLA) (2023). Rules for the Measurement and Inspection of Hardwood. nhla.com.
Standard rules for board-foot measurement of hardwood.
View source
This calculator is a reference tool, not a substitute for professional advice. Verify important health, financial, legal, or safety decisions with a suitably qualified professional.
Last updated: October 7, 2026
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Frequently Asked Questions
What is a board foot?
A board foot is a unit of lumber volume equal to 144 cubic inches — the volume of a board 1 inch thick, 12 inches wide, and 12 inches long. It's the standard way lumber is sold and priced in the US and Canada.
How do I calculate board feet?
Multiply thickness × width × length (all in inches) and divide by 12. For a 2×6 that's 8 feet (96 inches) long: (2 × 6 × 96) ÷ 12 = 8 board feet.
Are board feet based on actual or nominal size?
Nominal size — the labelled dimensions. A '2×4' is calculated as 2 in × 4 in even though its actual finished size is about 1.5 in × 3.5 in. This is standard lumber-industry practice.
How do I work out the cost of lumber?
Multiply the total board feet by the price per board foot. If hardwood is $6 per board foot and you need 40 board feet, the cost is 40 × $6 = $240. Enter your price in the calculator to get this automatically.