What is a Board Foot? Complete Guide to Wood Measurement

Last reviewed: November 8, 2025 by the Board Foot Calculator content editors.

If you’re new to woodworking or planning a lumber project, you’ve probably encountered the term “board foot” and wondered what it means. A board foot is the standard unit of measurement for lumber volume in the United States and Canada. The definition follows the USDA Forest Products Laboratory “Wood Handbook”, and understanding it is essential for accurate project planning and cost estimation.

In this guide, you’ll learn:

• The precise definition of a board foot
• How to calculate board feet using a simple formula
• Practical examples with common lumber sizes
• How board feet differ from other wood measurements
• Real-world applications in woodworking and construction

By the end of this 5-minute read, you’ll be confident in calculating board feet for any wood project.

Definition of Board Foot

A board foot is a unit of volume used to measure lumber. It represents the volume of a piece of wood that is:

• 1 foot long
• 1 foot wide
• 1 inch thick

This standard measurement equals 144 cubic inches of wood (12 inches × 12 inches × 1 inch = 144 cubic inches).

Why Use Board Feet?

The lumber industry uses board feet because it provides a standardized way to measure and price wood that accounts for thickness variations. Unlike linear feet (which only measures length) or square feet (which measures area), board feet measures volume — the actual amount of wood material.

This makes it easier to (see NHLA Grading Rules):

• Compare prices across different lumber sizes
• Estimate costs for projects accurately
• Calculate material needs for furniture and construction
• Manage inventory in lumberyards and warehouses

Understanding the Formula

The board foot formula is straightforward once you understand the units involved.

Formula Variables

Why Divide by 144?

The number 144 comes from converting the standard board foot dimensions to cubic inches, as outlined in the USDA Wood Handbook:

• 1 foot = 12 inches
• 1 foot × 1 foot × 1 inch = 12 in × 12 in × 1 in = 144 cubic inches

When you calculate the volume of your lumber in cubic inches (T × W × L, where L is converted to inches by multiplying by 12), dividing by 144 tells you how many standard board feet that volume represents.

Common Misconception

Many people confuse board feet with square feet because both involve “feet” in the name. Remember:

• Square feet measures area (2D) — length × width
• Board feet measures volume (3D) — length × width × thickness

A 10-square-foot area can contain different amounts of board feet depending on the wood’s thickness.

How to Calculate Board Feet

Let’s walk through three practical examples to master board foot calculations.

Example 1: Standard 2×4 Lumber

Calculate the board feet in a common 2×4×8’ piece of lumber.

Given:

• Thickness (T): 2 inches
• Width (W): 4 inches
• Length (L): 8 feet

Formula:

Board Feet = (T × W × L) / 144

Calculation:

Board Feet = (2 × 4 × 8) / 144
           = 64 / 144
           = 0.44 board feet

Important Note: This calculation uses nominal dimensions (the size the lumber is called). The actual dimensions of a 2×4 are approximately 1.5” × 3.5”, which would give:

Board Feet = (1.5 × 3.5 × 8) / 144 = 0.29 board feet

Always clarify with your supplier whether pricing is based on nominal or actual dimensions—a best practice recommended by both NHLA graders and the Woodwork Institute pricing guidelines.

Example 2: Wide Board (1×12)

Calculate board feet for a 1×12×10’ board, commonly used for shelving.

Given:

• Thickness (T): 1 inch
• Width (W): 12 inches
• Length (L): 10 feet

Calculation:

Board Feet = (1 × 12 × 10) / 144
           = 120 / 144
           = 0.83 board feet

Practical Application: If this board costs $5 per board foot, your cost would be:

Cost = 0.83 × $5 = $4.15

Example 3: Multiple Pieces

Calculate total board feet for a project requiring 5 pieces of 2×6×12’ lumber.

Step 1: Calculate board feet for one piece

Board Feet (1 piece) = (2 × 6 × 12) / 144
                     = 144 / 144
                     = 1.0 board foot

Step 2: Multiply by quantity

Total Board Feet = 1.0 × 5 pieces
                 = 5.0 board feet

Cost Estimation: At $4.50 per board foot:

Total Cost = 5.0 × $4.50 = $22.50

Practical Applications of Board Feet

Understanding board feet is essential for several real-world scenarios:

Wood Purchasing

When buying lumber, suppliers typically price wood by the board foot. Knowing how to calculate board feet helps you:

• Compare prices between different suppliers
• Verify quantities on invoices and receipts
• Negotiate bulk discounts based on total board feet
• Avoid overpaying for smaller quantities

Example: If Supplier A charges $4.50/BF and Supplier B charges $4.25/BF, buying 100 board feet saves you $25 with Supplier B.

Project Planning

Before starting a woodworking project, calculate the total board feet needed:

• Furniture building: Estimate lumber for tables, chairs, cabinets
• Home renovation: Calculate flooring, paneling, or trim needs
• Outdoor projects: Determine decking, fencing, or pergola materials
• Add 10-15% extra for cutting waste and mistakes

Cost Estimation

Board feet makes budgeting straightforward:

1. Calculate total board feet needed
2. Multiply by price per board foot
3. Add waste allowance (10-15%)
4. Include delivery fees if applicable

Budget Example:

• Project needs: 75 board feet
• Price: $5.50/BF
• Waste allowance: 10% (7.5 BF)
• Total: 82.5 BF × $5.50 = $453.75

Inventory Management

Lumberyards and woodworking shops use board feet to:

• Track stock levels across different lumber types
• Calculate storage space requirements
• Manage reorder points for popular sizes
• Standardize pricing across various dimensions

Board Feet vs Other Wood Measurements

Understanding the differences between measurement units helps you choose the right one for your needs.

Board Feet vs Cubic Feet

Board Feet:

• Standard for lumber pricing
• Uses mixed units (inches and feet)
• Formula: (T × W × L) / 144
• Example: 2×4×8’ = 0.44 BF

Cubic Feet:

• Measures pure volume
• Uses consistent units (all feet)
• Formula: (T × W × L) / 1728
• Example: 2×4×8’ = 0.037 cubic feet

When to Use: Board feet for lumber purchasing; cubic feet for shipping or storage volume calculations.

Board Feet vs Square Feet

Board Feet:

• Measures volume (3D)
• Accounts for thickness
• Used for lumber pricing
• Example: 1×12×10’ = 0.83 BF

Square Feet:

• Measures area (2D)
• Ignores thickness
• Used for flooring/paneling coverage
• Example: 1×12×10’ = 10 square feet

Key Difference: The same 10 square feet of coverage requires different board feet depending on thickness:

• 1” thick: 10 BF
• 0.75” thick: 7.5 BF
• 2” thick: 20 BF

Board Feet vs Linear Feet

Board Feet:

• Measures volume
• Accounts for width and thickness
• Used for pricing
• Example: 2×4×8’ = 0.44 BF

Linear Feet:

• Measures length only
• Ignores width and thickness
• Used for trim, molding, rope
• Example: 2×4×8’ = 8 linear feet

When to Use: Linear feet for items sold by length (trim, rope, chain); board feet for dimensional lumber.

Quick Reference Table

Use this table for instant board foot calculations of common lumber sizes:

Frequently Asked Questions

Why does the lumber industry use board feet instead of cubic feet?

Board feet provide a standardized measurement that’s easier to work with for lumber pricing and inventory. Since most lumber is sold in standard widths (4”, 6”, 8”, etc.) and thicknesses (1”, 2”), board feet simplify calculations. The mixed-unit system (inches for thickness/width, feet for length) matches how lumber is actually measured and sold in practice.

Additionally, board feet make it easier to calculate costs when you know that, for example, a 2×4 contains approximately 0.67 board feet per linear foot, regardless of length.

How do I quickly estimate board feet without a calculator?

For quick mental math, use these shortcuts:

Method 1 - The “12-foot rule”: For any lumber that’s 12 feet long, the board feet equals (T × W) / 12. For example, a 2×6×12’ = (2 × 6) / 12 = 1 BF.

Method 2 - Common sizes: Memorize these benchmarks:

• 2×4×8’ ≈ 0.5 BF (actually 0.44)
• 2×6×12’ = 1.0 BF (exact)
• 1×12×10’ ≈ 1.0 BF (actually 0.83)

Method 3 - Proportional scaling: If you know one size, scale proportionally. If 2×4×8’ = 0.44 BF, then 2×4×16’ = 0.88 BF (double the length, double the board feet).

Do nominal size and actual size affect board foot calculations?

Yes, significantly. Nominal size is what the lumber is called (like “2×4”), while actual size is the real dimensions after planing (1.5” × 3.5” for a 2×4).

For pricing: Most suppliers price based on nominal dimensions, so a 2×4 is charged as if it’s actually 2” × 4”.

For project planning: Use actual dimensions to ensure you have enough material. A 2×4 provides less wood than the nominal size suggests.

Example comparison:

• Nominal 2×4×8’: (2 × 4 × 8) / 144 = 0.44 BF
• Actual 2×4×8’: (1.5 × 3.5 × 8) / 144 = 0.29 BF

Always clarify with your supplier which measurement they use for pricing.

Does board foot calculation apply to all types of wood?

Yes, board feet is the standard measurement for all dimensional lumber, including:

• Softwoods: Pine, fir, cedar, spruce
• Hardwoods: Oak, maple, walnut, cherry
• Treated lumber: Pressure-treated outdoor wood
• Engineered wood: Plywood, MDF (though often sold by sheet)

However, some specialty products are sold differently:

• Plywood/OSB: Sold by the sheet (4’×8’)
• Trim/molding: Often sold by linear foot
• Logs: May use different volume measurements (cords, cubic meters)

For standard dimensional lumber from a lumberyard, board feet is universal.

How do I handle lumber with irregular dimensions?

For lumber with non-standard dimensions:

Step 1: Measure actual thickness, width, and length Step 2: Use the same formula: (T × W × L) / 144 Step 3: Round to practical precision (usually 2 decimal places)

Example - Live edge slab:

• Thickness: 2.25”
• Average width: 18” (measure at multiple points and average)
• Length: 7.5 feet

Board Feet = (2.25 × 18 × 7.5) / 144
           = 303.75 / 144
           = 2.11 board feet

For highly irregular pieces (like burls or slabs with varying width), measure width at several points and use the average.

Do I need to account for moisture content in board foot calculations?

For purchasing and pricing, no — board feet calculations use the physical dimensions regardless of moisture content. However, moisture content matters for:

Project planning: Wood shrinks as it dries. Green (wet) lumber may lose 6-8% of its volume when dried to standard moisture content (6-8%). Plan for this shrinkage in critical dimensions.

Weight calculations: Wet wood weighs significantly more than dry wood, affecting shipping costs.

Industry standards: Most lumber is sold at “kiln-dried” moisture content (6-8% for interior use, 12-15% for exterior). The board foot measurement is based on these standard conditions.

Best practice: Buy kiln-dried lumber for indoor projects to avoid warping and shrinkage issues.

Related Tools and Resources

Ready to put your knowledge into practice? Try these helpful tools:

Start Calculating Board Feet Today

Now that you understand what a board foot is and how to calculate it, you’re ready to tackle any woodworking project with confidence. Whether you’re building furniture, renovating your home, or simply buying lumber, board feet calculations will help you plan accurately and budget effectively.

Key Takeaways:

• A board foot = 1 ft × 1 ft × 1 in = 144 cubic inches
• Formula: Board Feet = (T × W × L) / 144
• Always clarify nominal vs. actual dimensions with suppliers
• Use board feet for lumber pricing, square feet for coverage area
• Add 10-15% extra for waste in project planning