This is How to Calculate Board Feet the Easy Way. When you buy wood, you need to understand the way that it is sold in order to be able to figure out the price. Calculating board feet can be intimidating at first, but I’ll make it really simple. Enjoy.
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What is a Board Foot?
The simplest way to think of a board foot is think of a piece of wood that is 1 inch thick, and 12“ x 12“ square. That one flat piece of wood that is a foot long, a foot wide, and 1 inch thick, is the base unit for measuring all other pieces of wood.
You will almost never find a piece of wood that looks like this in the pile. Also, don’t think of this is an actual piece of wood, just think of it as a three-dimensional measurement for wood that can be used to show the true amount of any piece, no matter the size, length or shape.
Now that you know what a board foot is, it’s time to learn why you need it.
See Also: What is a Board Foot?
Why do You Need it?
The problem with buying a natural product like wood is that it comes in a lot of different widths, thicknesses, and lengths. You can’t just price something like this by the linear foot, because what happens when pieces are different widths, or thicknesses?
Since pricing becomes such an issue, the board foot was developed to solve the problem. Basically what it does is mathematically converts every piece of wood into pieces that are 1 foot x 1 foot x 1 inch. Since all of the pieces are now the same, they can be given one price.
This means you will pay the same amount for any piece of wood based on its volume, and not in shape. This is a key distinction, because shape can be misleading, and that’s not good when it comes to buying things.
See Also: Linear Foot vs Board Foot Explained
How to Calculate Board Feet
When it comes time to calculate board feet, you really only need to have three measurements. You need to know the length of your piece of wood, the width, and the thickness. For the thickness, there’s one little piece of information that makes it all work really easily, and I’ll cover that first.
Wood is measured in nominal increments. This means a thickness of one is really closer to 3/4 of an inch. You need to use those whole numbers in your board foot calculation, which will be really obvious coming up in a second.
The last piece of the puzzle is remembering is the number 144. This is the number of cubic inches in one board foot. When we do the math on a piece of wood, will use this number to figure out how many board feet are there.
For example, let’s say you have a piece of wood that is 1 for the thickness thickness, and measures 58 inches long and 7 1/2 inches wide. The first step is to multiply all of these numbers together, which is 58 x 7.5 x 1 = 435.
Next, divide 435 by 144, which converts cubic inches into board feet. So, 435/144 = ~3. In this case, the piece of wood measures about three board feet. So, if the wood was $10 a board foot, you would be looking at a $30 piece of wood.
(When in doubt, ask the person in the store for the thickness measurement, or look at the tags, which will tell you)
See Also: 13 Myths About Getting Into Woodworking
Dealing With Thicker Pieces
The only time that you won’t multiply by one for the sickness is when you have thicker pieces of material. If a piece of wood is two by, then you would multiply by two. If it was four by, then you would multiply by four.
Most of the time, the woodworking store will be able to tell you the thickness factor, and that will help you quite a bit with your math. For example, a piece of wood that’s 8/4, or to by in thickness, is literally twice the price of the same board in 4/4.
Don’t let all of those numbers confuse you, or frustrate you, just think about the wood being twice as thick, so logically it’s twice as expensive. When the wood is four times a stick, it will be four times as expensive, because there is four times as much.
However, the vast majority of the time you are going to be dealing with pieces of wood that are standard 4/4 thickness. Just multiply your thickness as the number one, and you’re all set.
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The Board Foot Equation
If you like the mathematical side of things, here is an equation that you can write down that will help you remember how to calculate board feet. Keep it with you, and you’ll always know exactly how much wood you are buying.
BF = (L x W x T) / 144. Written out, this equation says that board feet equals the length times the width times the thickness, divided by 144.
The easiest way to do this is to always multiply your three size numbers together first, then divide that number by 144 to get your answer.
Since your answer is in feet, all you have to do is multiply that number and the price of the wood per board foot, and you’ll know exactly what to expect when you get to the cash register.
For example, if you have 2.5 board feet of Maple, and it’s $7 per board foot, you are looking at a bill of $17.50
Your Action Assignment
Now that you know how to calculate board feet, it’s time to get out in the shop and take action on what you learned. Rather than be embarrassed when you go to the wood store, get out your tape measure and start practicing on pieces of wood you already have.
Grab some random pieces, and get used to measuring their length and width and thickness. Use the calculator in your phone to multiply them together, and then divide that number by 144. In your head, multiply by a fictional price, and you’ll have an idea of the process.
Once you know how to do this, it’ll be a lot easier when the time comes in the store. You’ll also be able to use this to your advantage when picking out wood for your projects, so that way you don’t to buy more than you actually need.
If you have any questions on how to calculate board feet the easy way, please post a question and I’ll be glad to answer them. Happy building.
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