What is a board foot anyway?
This is a common question that we encounter, and unless you are a woodworker yourself or happen to work in the lumber industry, it’s unlikely that you would have ever used this measurement before. Measuring linear feet is straightforward enough—you pull the tape measure out and determine that a board is 12 feet long. But what if that board is 1 inch thick? Or 5 inches thick? What if that board is 3 inches wide? Or 12 inches wide? That’s where board feet come in.
Board Feet is a Measure of Volume
The simplest way to understand what a true “board foot” is (before we do any sort of calculating), is to know that:
One board foot = 1 inch thick x 12 inches wide x 12 inches long
This is easy enough to visualize: a 12-inch square piece of wood that is 1 inch thick is 1 board foot. If you double any one of those dimensions, you will have 2 board feet:
2 inches thick x 12 inches wide x 12 inches long = 2 board feet
1 inch thick x 24 inches wide x 12 inches long = 2 board feet
1 inch thick x 12 inches wide x 24 inches long = 2 board feet
If you double two of those dimensions at the same time, you will have 4 board feet:
2 inches thick x 24 inches wide x 12 inches long = 4 board feet
2 inches thick x 12 inches wide x 24 inches long = 4 board feet
1 inch thick x 24 inches wide x 24 inches long = 4 board feet
And if you double all three of those dimensions at the same time, you will have 8 board feet:
2 inches thick x 24 inches wide x 24 inches long = 8 board feet
How to Calculate Board Feet
Now that you can visually comprehend what a board foot is, let’s learn how to math it out! First, measure the thickness, width, and length of your piece of wood, making sure to use inches for all three measurements. Then, divide that number by 144 to get your board feet measurement. You divide by 144 because there are 12 inches in a foot, and 12 squared is 144. This is the formula:
Thickness (inches) x Width (inches) x Length (inches) / 144 = Board Feet
Oftentimes, you will be measuring a board that is much longer than it is wide or thick. So, you might measure the length in feet rather than inches. If you choose to measure the length in feet, you can divide by 12 instead of 144 because one of your measurements is already converted to feet. So, you use this formula:
Thickness (inches) x Width (inches) x Length (feet) / 12 = Board Feet
Personally, I prefer to keep all my measurements in the same unit—inches. Especially when you are the one milling the wood, you rarely end up with boards that are exactly 8 feet long, 9 feet long, etc. Also, tape measures conveniently display the total number of inches, allowing you to easily see that a board is 96 inches long instead of 8 feet. This makes it easier for me to measure and calculate accurately.
Understanding board feet is essential for any woodworker or lumber industry professional. It helps ensure accurate calculations and efficient use of materials. Happy woodworking!
