Lumber calculator

Understanding Lumber Measurements: Board Feet vs. Linear Feet

When working with lumber, understanding the difference between board feet and linear feet is essential for accurate project planning and cost estimation. These two measurement systems serve different purposes in woodworking and construction.

What is a Linear Foot?

A linear foot is a straightforward measurement of length. One linear foot equals exactly 12 inches of length, regardless of the wood’s width or thickness. This measurement is particularly useful when you need pieces of consistent dimension, such as trim, molding, or deck boards sold by length.

What is a Board Foot?

A board foot is a volume measurement used specifically for lumber. One board foot equals:

• 1 foot in length
• 1 foot in width
• 1 inch in thickness

This translates to 144 cubic inches of wood (12″ × 12″ × 1″). Board foot measurements are standard for hardwoods and dimensional lumber, as they account for all three dimensions of the wood.

When to Use Each Measurement

Use linear feet when:

• Purchasing materials like trim, molding, or decking
• The width and thickness are consistent across pieces
• You’re primarily concerned with length requirements

Use board feet when:

• Working with hardwoods or rough lumber
• The width and thickness vary between pieces
• You need to calculate the total volume of wood required
• Comparing prices between different lumber suppliers

Practical Examples

Let’s consider some real-world examples:

Example 1: A 1×6 board that’s 8 feet long contains 4 board feet: (1″ × 6″ × 96″) / 144 = 4 board feet.

Example 2: A 2×4 that’s 12 feet long contains 8 board feet: (2″ × 4″ × 144″) / 144 = 8 board feet.

Example 3: A piece of oak measuring 1.5″ thick, 9″ wide, and 6 feet long contains 6.75 board feet: (1.5″ × 9″ × 72″) / 144 = 6.75 board feet.

Lumber Terminology Glossary

Tips for Accurate Lumber Calculations

• Always measure twice and calculate once to minimize errors
• Consider adding 10-15% extra lumber for waste, especially for complex projects
• Verify whether your supplier uses nominal or actual dimensions in their pricing
• Check moisture content if working with projects requiring dimensional stability
• Understand the difference between rough and finished lumber dimensions

Example 1: Deck Building

Imagine you’re building a 12′ × 16′ deck using 2×6 boards:

• Deck area: 192 square feet
• Using 16-foot long boards
• Spacing: ¼” between boards

Calculation: You’ll need approximately 24 boards (16 linear feet each) for a total of 384 linear feet. In board feet: (2″ × 6″ × 384′) / 12 = 384 board feet.

Example 2: Bookshelf Project

Building a simple 3-shelf bookcase from 1×12 pine:

• Shelves: 3 pieces at 36″ long
• Sides: 2 pieces at 72″ long
• Total linear feet: (3 × 3′) + (2 × 6′) = 21 linear feet

Calculation: Board feet calculation: (1″ × 12″ × 252″) / 144 = 21 board feet. Always add extra for mistakes – purchase 25 board feet.

Example 3: Hardwood Table Top

Creating a dining table top from 8/4 walnut:

• Dimensions: 42″ × 84″ × 2″ thick
• Using boards averaging 8″ wide
• Approximately 6 boards needed

Calculation: Total board feet: (2″ × 42″ × 84″) / 144 = 49 board feet. With waste, purchase 55 board feet of walnut.

Example 4: Picture Frames

Making 10 picture frames from 1×2 poplar:

• Each frame: 4 pieces at 24″ long
• Total length: 10 frames × 4 pieces × 2′ = 80 linear feet

Calculation: Since this is sold by linear foot, you’d purchase 80 linear feet of 1×2 poplar. In board feet: (1″ × 2″ × 960″) / 144 = 13.33 board feet.

1. Understanding Lumber Grades

Lumber is graded based on quality and appearance:

• FAS (First and Second): Highest quality, suitable for furniture
• Select: Good appearance with minor defects
• #1 Common: More defects but usable for many projects
• #2 Common: Contains knots and defects, suitable for painting
• Construction Grade: For structural applications where appearance doesn’t matter

2. Moisture Content Considerations

The moisture content of lumber affects its stability:

• Green lumber: High moisture content (over 30%), requires drying
• Air-dried: Moisture content around 15-20%
• Kiln-dried: Moisture content 6-8%, ideal for indoor projects
• For furniture, use kiln-dried wood to prevent warping
• For outdoor projects, pressure-treated lumber has higher moisture content

3. Calculating Waste Factor

Always purchase extra lumber to account for:

• Cutting mistakes
• Natural defects in the wood
• Unexpected project changes
• Future repairs

Recommended waste factors:

• Simple projects: 10% extra
• Complex projects: 15-20% extra
• Projects with many cuts: 25% extra
• When working with expensive hardwoods: 30% extra to allow for selective cutting

4. Price Comparison Tips

When comparing lumber prices:

• Convert all prices to board feet for accurate comparison
• Consider delivery costs if purchasing large quantities
• Check for volume discounts when buying larger quantities
• Factor in the time and cost of preparing rough lumber
• Remember that higher-grade lumber costs more but may yield better results
• Consider the true cost including waste factor

Our lumber calculator helps you make these comparisons accurately by providing both linear feet and board feet measurements.

Why is there a difference between nominal and actual lumber dimensions?

Nominal dimensions refer to the size of the wood before it’s dried and planed. The drying process causes shrinkage, and planing smooths the surfaces, reducing the actual dimensions. For example, a 2×4 nominally measures 2″ by 4″, but its actual dimensions are approximately 1.5″ by 3.5″.

How do I calculate board feet for irregular-shaped wood?

For irregular pieces, calculate the volume by measuring the average width, thickness, and length. Multiply these three dimensions and divide by 144 to get board feet. For very irregular pieces, you might need to use water displacement methods to determine volume.

Should I use linear feet or board feet when purchasing lumber?

It depends on the type of project and lumber. Use linear feet for dimensional lumber with consistent cross-sections (like 2×4s or deck boards). Use board feet for hardwoods or when the width and thickness vary significantly between pieces.

How much extra lumber should I buy for waste?

The amount of extra lumber needed depends on the project complexity and your experience level. For simple projects, add 10% extra. For complex projects with many cuts, add 15-20%. When working with expensive hardwoods or intricate designs, consider 25-30% extra to allow for selective cutting and mistakes.

Why is lumber priced differently per linear foot versus per board foot?

Pricing per linear foot is simpler and common for dimensional lumber with consistent cross-sections. Pricing per board foot accounts for the actual volume of wood, which is more accurate for hardwoods and rough lumber where dimensions can vary significantly.

How does moisture content affect lumber calculations?

Moisture content affects the weight and dimensions of lumber. Wood shrinks as it dries, so projects requiring precise dimensions should use kiln-dried lumber (6-8% moisture content). For outdoor projects, pressure-treated lumber has higher moisture content but is resistant to rot and insects.

Mobile-Friendly Features

• Touch-friendly input fields and buttons
• Responsive design that works on all screen sizes
• Quick unit conversion for on-the-fly calculations
• Visual lumber representation adjusts to your dimensions
• Share results directly from your mobile device

Tips for Mobile Use

• Bookmark the calculator for quick access at lumber yards
• Use the share feature to send calculations to colleagues
• Take screenshots of results for reference while shopping
• Switch between units to match how your supplier prices lumber
• Use the refresh button to quickly start new calculations