how do i calculate board feet (as opposed to linear feet)
Edited 6/21/2005 2:33 pm ET by Tim
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Edited 6/21/2005 2:33 pm ET by Tim
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A board foot of lumber is the amount of wood in a board 12" long by 12" wide by 1" thick (e.g. 4/4). Such a board would have a surface area of 144 (sq) inches, and would be 1 inch thick, or 144 cu inches total.
Since most lumber is measured in inches, the way to think of this is to calculate the "volume" of lumber in cubic inches and then divide by 144 to get bf.
For example, to calculate the board feet at a mill, take all the boards of the same thickness and total them together, calculate the area and multiply by the thickness, then divide by 144. So, suppose your cut list consists of 4 boards that are 4/4, 5/4 and 8/4 in thickness:
5.5"x72"x4/4, 7"x66"x4/4, 6.5"x49"x5/4 and 4.5"x59"x8/4.
The 4/4 boards are 5.5x72+7x66=396+462=858; x 4/4=858.
The 5/4 board is 6.5x49=318.5; x 5/4=398
The 8/4 board is 4.5x59=265.5; x 8/4=531
The total lumber is 858+398+531=1,787; divide by 144 to get board feet: 1787/144=12.4 board feet. If the wood is $5.35/bf, then you pay 12.4x5.35, or $66.34.
Glaucon
If you don't think too good, then don't think too much...
You my old MATH TEACHER?
Damn straight- you still owe me a make up trig exam. You have until Friday.Glaucon
If you don't think too good, then don't think too much...
thank you
What are the actual thicknesses of nominal measurements like 4/4, 5/4 and 8/4? ie, does 4/4 nominal mean 3/4" actual thickness or 1" actual thickness?
Tim ,
The terms 4/4 , 5/4 , 8/4 refer to the lumber in the rough , so when cut 4/4 is one inch thick 5/4 is one and a quarter inch and 8/4 is two inches thick before surfacing to finished lumber . The finished dimensions can vary .
hope this helps dusty
thank you
"What are the actual thicknesses of nominal measurements like 4/4, 5/4 and 8/4? ie, does 4/4 nominal mean 3/4" actual thickness or 1" actual thickness?"
Tim,
Measurements expressed in quarters, e.g. 4/4, are the dimensions used (sawn-to) at the sawmill, and refer to the thicknesses specified on the sawyers' cut sheet.
Surfaced wood, e.g. S4S, may be nominally 4/4 thickness, but has usually been milled to approximately 3/4" during the commercial planing process.
Squaring and sizing rough-sawn lumber yourself can save money in two ways:
The selling price per board-foot is lower for rough-sawn than for lumber that has undergone additional processing;
through careful selection, pre-sizing, and squaring, your can achieve a higher yield per purchased board-foot (when I mill it myself I can often get close to a full inch of thickness out a 4/4 rough sawn board).
EXAMPLE: Start with a rough-sawn board containing 144 cubic inches of wood fiber:
If factory milled to 3/4" actual thickness your yield is 75% on boards that cost you more to begin with;
If you mill it yourself and achieve 7/8" actual thickness, the yield per useable board-foot increases to 87.5% and the cost per useable board-foot remains less than for factory-surfaced lumber.
By the way, when performing board-foot calculations:
When the thickness of a rough-saw board is less than 4/4, it is considered one-inch in thickness when performing board-foot calculations - the difference in thickness is accounted for in the cost per board-foot.
When calculating board footage, if the thickness is 4/4, it is not necessary to include it in board-footage calculations because 4/4 = 1.
-Jazzdogg-
Whether you think you can, or you think you can't, you're right.
Edited 6/21/2005 5:40 pm ET by jazzdogg
Edited 6/21/2005 5:42 pm ET by jazzdogg
Thank you, very informative, excellent explanation
You're welcome, Tim.-Jazzdogg-
Whether you think you can, or you think you can't, you're right.
yes but.... Isn't the rough 4/4 BEFORE drying? And won't this reduce the 4/4 to something slightly smaller.
"...we mutually pledge to each other our Lives, our Fortunes and our sacred Honor."
"Kill'em all and let Allah sort them out."
4/4 wood is not a wet or dry measure. It is a measure of the finished product. 4/4 boards will after drying and surfacing and allowing for grade be 13/16" (3/16" under the nominal.)Somewhere around 8/4 the amount under nominal increases to 1/4".
"yes but.... Isn't the rough 4/4 BEFORE drying? And won't this reduce the 4/4 to something slightly smaller."
Scarecrow,
I apologize if I wasn't clear enough when I said: Measurements expressed in quarters, e.g. 4/4, are the dimensions used (sawn-to) at the sawmill, and refer to the thicknesses specified on the sawyers' cut sheet, as I thought most people would understand that lumber is typically dried following sawmill operations.
When we use the Woodmizer - as suggested by the use of quarter-inch increments - we are approximating thicknesses, and when we saw, tend to err on the side of generosity - that isn't as likely in for-profit organizations as it is in non-profits and schools.
Of course, ultimate yield is a function of both the way boles are sawn and careful selection by the end user. That being said, I still believe one can obtain better yield and lower lumber cost-of-sales when starting with rough lumber.
Post-sawmill processing of rough lumber consumes labor, the cost of which is ultimately added to the project cost, and the methodologies endemic to a specific operation have to be taken into account to determine whether the added labor makes economic sense in each instance.
-Jazzdogg-
Whether you think you can, or you think you can't, you're right.
Edited 6/21/2005 7:41 pm ET by jazzdogg
Of course, ultimate yield is a function of both the way boles are sawn and careful selection by the end user. That being said, I still believe one can obtain better yield and lower lumber cost-of-sales when starting with rough lumber.
Without a doubt, but the 4/4 I see at my local lumber supplier is always "just" shy 1 inch. I assume it's due to the drying process.
"Kill'em all and let Allah sort them out."
"Religion doesn't kill people, people kill people."
"...we mutually pledge to each other our Lives, our Fortunes and our Sacred Honor."
Scarecrow,
YES! Wood shrinks as it dries, which helps to explain why commercially-sawn 4/4 rough lumber may be a skosh under a measured inch in thickness after drying; their profits depend on achieving a balance between maximizing yield and what the market will tolerate.-Jazzdogg-
Whether you think you can, or you think you can't, you're right.
But I do agree with you that you get a better price/product if you mill it yer self as opposed to buying S4S.
"Kill'em all and let Allah sort them out."
"Religion doesn't kill people, people kill people."
"...we mutually pledge to each other our Lives, our Fortunes and our Sacred Honor."
Excellent information from all, but this begs the question...When buying rough sawed lumber, how much thickness should be accounted for surfacing? Say if I want a 1" board, does taking an 1/8" off of each side of a 5/4 leave me with a good surface at 1"?
No hard and fast rules for that, depends on how carefully you select the brd. If it has a lot of bow and or cup you may have to tak alot off and barely get 3/4 out of it.
Select wisely is the key.
"Kill'em all and let Allah sort them out."
"Religion doesn't kill people, people kill people."
"...we mutually pledge to each other our Lives, our Fortunes and our Sacred Honor."
In a perfect world you should get 3/4" off a 1" R/S board, however this depends on a number of factors such as bow, warp & length of required piece, as well as the generousity of the sawyer. I find that by having a good relationship with my timber yard (located 250 miles away) & giving them an idea of minimum lenghths I can get what I want which sometimes can be as much as 7/8".
Just recently did a job in (US Sourced) Black Walnut & was really working to get 3/4" while another in NZ sourced Montery Pine could easily yield 15/16".
Also if you cut to length early in the milling operation you will have more opportunity to get your desired thickness as you will have a better chance to dress out a warp or bow.
Don
Your 5/4 should surface clean at 1-1/16".
CTB,
Downunder and GeorgeR are correct. If you are really lucky, have a strategy to maximize thickness, and are careful during processing, you may be able to obtain stock as thick as 7/8" or even 15/16" from 4/4 rough-sawn stock.
Virtually all furniture and cabinet makers who select their own stock will achieve 3/4" and many will achieve 7/8" from rough-sawn 4/4. If you buy sight unseen, your chances go down unless you are dealing with a sawyer or reseller who has your best interests in mind and selects stock based upon well-considered specifications provided by you.
If you want to assure a full 4/4" thickness after squaring, your best bet is to buy 5/4" stock to begin with. Bear in mind that a great deal of factory-planed (e.g., S4S) stock has to be re-squared before it can be used in fine woodworking; even if you buy S4S, you would be wise to purchase stock that is thicker and wider than the finished dimensions you need for your project.
When you chalk out your parts on rough stock, look for more than coloration and grain; think about the minimum stock sizes your machines will accommodate. For example, the distance between the infeed and outfeed rollers on thickness planers and finishing sanders will determine the minimum length of stock that they can handle; if your stock needs to be at least 18" long for your thickness planer, you can maximize yield by rough cutting to pieces down to at least 18" in length before squaring.
Additionally, the size of your jointer may impose limitations - if you have a 6" or 8" jointer, reduce the width of your stock to before squaring. When face jointing rough stock, the objective is to remove only enough stock to allow the jointed face to rest flat and square on the infeed table of the thickness planer - there is no need to joint the face absolutely flat; both faces are generally flattened during thicknessing. If there is a low section that's still rough after jointing and planing , double check against your cut list to see of you can work around questionable areas, instead of sacrificing thickness to achieve arbitrary flatness.
When dealing with stock that is warped (crook, cup, bow, etc.), you can sometimes maximize thickness by ripping and crosscutting the stock into smaller pieces at the bandsaw and gluing them back together after squaring.
I hope this helps,
-Jazzdogg-
Whether you think you can, or you think you can't, you're right.
Thanks for the Replies Jazzdog, Downunder, GeorgeR and Scarecrow.Excellent feedback and advice on surfacing; you have given me some additional things to think about and look for when selecting stock.
You're welcome.
Sawdust in your shoes,-Jazzdogg-
Whether you think you can, or you think you can't, you're right.
calculating bd. ft.
Width in inches X length in ft. divide by 12.
A 4/4 board 9" wide, 9 ft long will have 6 3/4 bd. ft.
9 X 9 = 81 81 divided by 12 = 6 3/4 If it's an 8/4 plank it will contain 13 1/2 bd. ft. etc.
Here's the formula I use. width in inches X thickness in inches X length in feet and divide by 12. Same result, but a seems a little more straightforward to me.
"width in inches X thickness in inches X length in feet and divide by 12. Same result, but a seems a little more straightforward to me."
Bldrbill,
That method works just as well - as long as you are buying boards that aren't odd lengths. I find that the higher the cost per board-foot, the more likely the seller is to measure length to the nearest inch.-Jazzdogg-
Whether you think you can, or you think you can't, you're right.
I think your method works fine, and I've used it. I favor mine for a couple of reasons. First, as another has pointed out, more expensive lumber tends to be measured to the inch. Second, I like to measure to the inch while I inspect the boards for checks and sapwood. This helps me know whether the wood can be cut for my project. For example, if I'm making a cabinet with 36" sides, and a cherry board is 76" long, with a check 37" from the end, I can buy and use that board; if the check is 28" from the end, I won't be able to use it for the sides of the cabinet.Glaucon
If you don't think too good, then don't think too much...
Whats all that have to do # bd. ft. in a board/plank. The originaal question was " how to figure bd. ft". Don't matter if the board / plank is twisted, bowed , warped, got checks, sap wood ,knots etc. All that doesn't change the # of bd. ft in piece of wood. Now if you're talking "usuable" bd.ft. in a piece, that's a tad different.Be not afraid of going slowly. Be afraid only of standing still. chinese proverb
This may be of some help for you.
Go to http://www.woodworkersweb.com/woodcalc.htm
There is an online program there called the Footulator that calculates board feet.
I buy a lot of lumber, frequently 200 bf at a time. Rather than doing the math and risking mistakes I use a calculator. Any of the Big Boxes sell a multifunction inch/foot calculator that figures board feet. It costs less than 20 bucks.
Mike
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