Board Foot Calculator: How to Accurately Measure Lumber

Have you ever gone to a lumberyard to buy wood for a deck or furniture project, only to have your eyes pop out when you saw the bill? It’s happened to us too. The price of lumber can seem confusing, especially when you see terms like “board foot” on the invoice. Not understanding this can lead to overspending, and sometimes you end up with too much or too little wood.

If you understand what a board foot is and learn how to use a simple Board Footage calculator, you’ll save a lot of money, avoid waste, and buy exactly the right amount of lumber.

In this guide, we’ll cover some important things, starting with: What exactly is a board foot? Then we’ll explain the simple formula. And much more that will be helpful to you.

If you don’t want to do the calculations manually, that’s okay. We’ll show you how to use this Free Online Board Foot Calculator. It’s very easy.

To understand lumber pricing, it’s also important to know how lumberyards price hardwood. They have a different approach.

Finally, we’ll give you some smart tips so you can confidently buy lumber next time. Whether you’re an experienced woodworker or a new DIY enthusiast, learning how to use a board foot calculator is essential for every successful project. Let’s get started!

What Is a Board Foot?

A board foot is a standard unit of volume for lumber, commonly used in the United States and Canada. Imagine a board that is one foot long, one foot wide, and exactly one inch thick. The volume of that board is what is called one board foot. Mathematically, this is equal to 144 cubic inches. This is completely different from a square foot, which only measures surface area. A board foot measures the entire volume, including thickness, not just length and width. This becomes very important when you are buying hardwood lumber, as hardwoods usually come in random sizes, meaning the width and length are not fixed.

The history of this unit is tied to the North American lumber trade. There, softwoods like pine and spruce were available in fixed sizes, but the size of hardwoods varied considerably. To bring consistency to buying and selling, the board foot system was developed. Therefore, it is also written as FBM, BDFT, or BF, and is still used today in the hardwood industry almost worldwide.

The most common confusion is that people mistake a board foot for a linear foot or a square foot. However, the difference is clear: a linear foot is just length, a square foot is area, and a board foot is a measurement of the entire volume. To clear up this misconception, consider an example: a 2x4x8 board. People often think that this would be 2 board feet per linear foot, but that’s not the case. If you calculate the total volume of the entire board, it comes out to roughly 5.33 board feet. This is because you have to include the thickness (which is 2 inches) in the calculation.

The Board Foot Formula Explained Step by Step

The formula for calculating board feet is very simple: Board Feet=Thickness (in)×Width (in)×Length (ft)/12

• In this system, thickness and width are measured in inches.
• And length is measured in feet.

Let’s understand this with some real-life examples:

• Example 1: 1x6x8 board
  • Board Feet=1*6*8/12=4BF
• Example 2: 2x4x10 board
  • Board Feet=2*4*10/12=6.67BF
• Example 3: 5/4x12x16 board (5/4 is 1.25 inches)
  • Board Feet=1.25*12*16/12=20BF

When working with rough lumber, always consider its actual thickness, not the nominal size. However, if the lumber has been surfaced or planed smooth, round its thickness to the nearest quarter-inch, such as 4/4, 5/4, etc. The most common mistakes here involve mixing units, such as combining inches and feet, or forgetting to divide by 12. Paying a little attention will easily prevent this confusion.

How to Calculate Board Feet Manually (with Examples)

To manually calculate board feet, follow these steps:

• Measure the length in feet.
• Measure the width in inches.
• Measure the thickness in inches.
• Multiply all three numbers together.
• Divide the result by 12.

For example, a piece of lumber that is 8 feet long, 10 inches wide, and 1.25 inches thick: Board Feet=8*10*1.25/12=8.33BF

To get the total board footage, multiply by the number of pieces of lumber. Lumber yards often round up or down for counting purposes, so always verify how they measure and charge.

Board Feet vs. Linear Feet vs. Square Feet

Measurement	What It Measures	When to Use
Board Feet	Volume	Hardwood lumber, custom projects
Linear Feet	Length	Trim, molding, uniform boards
Square Feet	Area	Flooring, decking, plywood

When buying hardwood lumber, board feet are used for boards of varying widths and thicknesses. Linear feet are used for boards of uniform thickness, and square feet are used for area-based projects.

Tips to Save Money When Buying Lumber

• To save on processing fees, buy rough lumber and have it milled yourself.
• Understand moisture content and grading thoroughly beforehand, as drier, higher-quality wood is more expensive.
• Negotiate with lumber yards by providing your own board foot calculations.
• For smaller projects, buy cut-offs or leftover pieces, as these are often discounted.
• Compare prices between suppliers based on the price per board foot, rather than per piece.

Taking accurate measurements, especially with a board foot calculator, is the foundation of every woodworking or construction project. If you understand the board foot formula and how lumber suppliers price hardwood, you can avoid costly mistakes and get the best value for your money.

Taking accurate measurements, especially with a board footage calculator, is the foundation of every successful woodworking or construction project. If you understand the board foot formula and how lumber suppliers price hardwood, you can avoid costly mistakes and get the best value for your money.

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If you’ve recently completed a project using board foot calculations, please share your experience in the comments!

Frequently Asked Questions