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Board foot calculations

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Forum topic by dan_fash posted 04-17-2015 07:01 PM 936 views 0 times favorited 14 replies Add to Favorites Watch
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dan_fash

62 posts in 2889 days


04-17-2015 07:01 PM

Hey LJ’s. Hoping for some simple help.

I’ve been building furniture for about 3 years now, but hav always bought wood from the box stores, and have never done board foot calculations for a big project.

I’m building a dining table, with a 1.5 inch thick 40×75 in top
the base is very similar to the pic ive attached, with the members 3” square

Included is a single bench with tob 16×70x1.5, and similar styled base

My calculations bring me to about 90 board ft (included 20% for waste)

I’m not too comfortable with that total, could anyone give me an idea if this sounds reasonable?

-- "If I find in myself a desire which no experience in this world can satisfy, the most logical explantion is that I was made for another world." -C.S. Lewis


14 replies so far

View SirIrb's profile

SirIrb

1239 posts in 694 days


#1 posted 04-17-2015 07:07 PM

Google store, free app called “wood working utilities”. It will spit out bdft based on thk x wdt x length.

Simply it is just a volume measure of 144 cu/in.

1.5 inch thick 40×75 in top: 41.67
1.5×16×70x: 15.56

-- Don't blame me, I voted for no one.

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dan_fash

62 posts in 2889 days


#2 posted 04-17-2015 07:33 PM

My concern is all the calculations for the base…

-- "If I find in myself a desire which no experience in this world can satisfy, the most logical explantion is that I was made for another world." -C.S. Lewis

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Yonak

979 posts in 984 days


#3 posted 04-17-2015 07:36 PM

Irb, I got 31.25 bf for the table top – (40 X 75 X 1.5) / 144 – and 11.66 bf for the bench top. If you’re including 20% for waste it comes to 37.5 bf and 14 bf. Am I wrong ?

dan, regarding the base, since there are no dimensions to go by, when calculating the lengths of the 3X3s (are you sure they’re not 4X4s ?), measure the longest distance for the angled pieces, or to the middle of the angles if you plan to double up on the angled cuts, which would be economical, and would be recommended. It seems like your calculation of 90 sounds a bit high, even adding the 20%. For the table, there are only about 2 bf in each of the two uprights and about 3.33 bf in each of the aprons and the stretcher (if 2” thick).

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Fred Hargis

3938 posts in 1956 days


#4 posted 04-17-2015 07:41 PM

You shouldn’t figure using the finished dimensions. To make 1.5” stock, you’ll probably have to buy 8/4, it’s possible that 6/4 can be finished out to 1 1/2”, but it will be risky…..and I’ve not seen 7/4 (though it may exist somewhere). So if I’m right about the 8/4, the top alone will take over 60 bd. ft., but I think your 20% extra is optimistic as well, maybe more for safety. Without knowing more about the wood needed for the base, it’s hard to estimate that, but it may have to be glued up from thinner stock like 8/4 (or maybe 12/4). The board foot of lumber you buy will have the waste included, even if they finish plane it at the supplier.

-- Our village hasn't lost it's idiot, he was elected to congress.

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Logan Windram

303 posts in 1925 days


#5 posted 04-17-2015 08:36 PM

Why not lighten up that design, save yourself some wood? Just a thought. It’s stylistic, but there is no reason that table has to be so bulky… I think you could literally use 1/2 the wood of not less…

Anyway, Apple Store has an app for board feet calculations. Board feet is hard to nail down. I use a lot of Ash, but only use the rift, so I waste a lot of flat sawn. You have to be discriminating and buy extra because of defects, color issues, etc.

3 inch square boards out of solid wood might be darn near impossible. 12/4 in my experience yields less that 3”, sometimes by a lot. Since your pieces are short you will be able to get more of the board with less to joint and plane.

I’d do a cut list with rough dimensioning to help build a strategy for stock purchase. Don’t be afraid to but extra, you’re a wood addict now, and wood addicts always build more.

Good luck

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dan_fash

62 posts in 2889 days


#6 posted 04-17-2015 08:57 PM

for the base, because of bord foot cost, I plan on buying 1.5 inch, and gluing up the pieces. for the top, I’ll be happy starting with 6/4 stock, knowing I’ll loose some in the finished pieces. attached is a pic of one of my table tops in pine, that gives an idea of the visual weight I’m hoping for. For the pic, I started with box store 2×6’s, so I feel like startign with 6/4 oak I should get the same impact.

-- "If I find in myself a desire which no experience in this world can satisfy, the most logical explantion is that I was made for another world." -C.S. Lewis

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AandCstyle

2569 posts in 1720 days


#7 posted 04-17-2015 11:36 PM

You might not be able to find 6/4 oak and if you do, it will measure closer to 1 3/8 by the time it is surfaced. To get 1.5” stock, you would have to buy 8/4 and plane it to 1.5”. This means that you will lose 25% to waste just in the thicknessing process, not to mention any other defects that will be present, although maybe other minor defects aren’t an issue with rustic pieces. FWIW

-- Art

View ElChe's profile

ElChe

630 posts in 799 days


#8 posted 04-18-2015 03:55 AM

Create a cut list and tape measure and chalk in hand go select the boards you are going to use. I’ve never found estimating board feet to give me a real accurate estimate of what I need. But checking off what you need as you select boards always works for me.

-- Tom - Measure twice cut once. Then measure again. Curse. Fudge.

View bbasiaga's profile

bbasiaga

756 posts in 1458 days


#9 posted 04-18-2015 04:04 AM

If you get decent with Google Sketchup, (free), there is a plugin called cutlist that will tell you the board feet. It also lays the pieces out on actual boards so you can get an idea of one way to cut them out. I always buy 20-30% more just to account for waste/errors.

-Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View hotbyte's profile

hotbyte

842 posts in 2439 days


#10 posted 04-18-2015 01:00 PM

I recently went through this for first time on, ironically enough, a table build. I used Sketchup and Cutlist to get an estimate of BF required. But, keep in mind the rough cut boards at lumberyard are not going to match the precise board size cutlist uses. The best advise I can add is study your plans closely, whether hand drawn or Sketchup, sp when you are picking out boards you can envision how each board will work in the plan. And, as mentioned, buy extra. It can always become the next smaller project :)

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helluvawreck

23161 posts in 2330 days


#11 posted 04-18-2015 01:28 PM

You will always have more waist than you think that you will with rough Lumber. Also, as pointed out you will need to figure the true thickness of rough lumber – usually 4/4, 5/4, 6/4, 8/4. You can get it thicker. If you can pick it out you can get a thick enough 6/4 piece that may yield close to 1-1/2 (maybe 1-4/16) if it is a good straight piece. We used to have a molding plant and got our lumber in by the tractor trailer load. We were always careful to pick out these thicker pieces in order to save money when we were able.

helluvawreck aka Charles
http://woodworkingexpo.wordpress.com

-- If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away. Henry David Thoreau

View dan_fash's profile

dan_fash

62 posts in 2889 days


#12 posted 04-18-2015 05:47 PM

Well, I found 6/4 red oak for $1.40/bft, which seems like a heck of a price, so I bought 100 bft. Would have bought more, but that was every stitch they had save 2

-- "If I find in myself a desire which no experience in this world can satisfy, the most logical explantion is that I was made for another world." -C.S. Lewis

View Wildwood's profile

Wildwood

1882 posts in 1598 days


#13 posted 04-18-2015 07:23 PM

When looking at a plan to build something always look at total number of feet of wood needed by lengths, widths, and thickness.

Big box stores & lumber yards sell a lot of softwood and hardwood lumber by Lineal foot, (nominal size) price is based upon length of the lumber regardless of width & thickness! Figuring total linear feet needed for a project little easier because simply add total number of feet needed for the project by length, width, & thickness of boards required. Some plans break that info down for you!

See chart for nominal sizes.

http://sawdustmaking.com/Free%20Charts/Lumber%20Dimension.pdf

When buying by the board foot you use length x width x thickness then divide the total by 144! When buying by the board foot width & thickness always rounded up! So bring a ruler to check length, width and thickness!

A board that is 96” long x 6” wide x 1” thick = 576
576 divided by 144 = 4 board feet

That board may well be 96” in length x 5 1/2” or 5 ¾” wide, and 4 quarter or 1” thick. You will still pay for 4 BF because they always round up to the next number.

If took a nominal size board from the big box or lumber yard and used the same formula 96” x 5 1/2” x ¾” actual size would end up with just 2.75 BF but rounded up to 3 BF.

Whether buy by lineal foot or board foot really depends upon you and what you are building, wood species, final finish, and time for completing the project etc. Still have to sort through the stack to find best boards.

That Red Oak sounds like a good deal!

-- Bill

View Yonak's profile

Yonak

979 posts in 984 days


#14 posted 04-18-2015 09:15 PM


If took a nominal size board from the big box or lumber yard and used the same formula 96” x 5 1/2” x ¾” actual size would end up with just 2.75 BF but rounded up to 3 BF.

- Wildwood

The thing is, the big box store is selling finished lumber (S4S). You will still pay for 4 bf for such a board. Wildwood, maybe you’re inferring this but I just wanted to clarify the different board foot tally between rough sawn and finished lumber.

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