Did I do this right -- board foot calculation?

[M Smith]

Hi all,

First time posting here, been lurking for a little while. Seems like a very friendly forum. I'm glad I found you all.

I *thought* I knew how to calculate board feet. I did do a search on this and read the corresponding threads, but I need help calculating the specific board foot for a small project of mine. I have the materials list, with dimensions, and did my calculations, but the wood supplier responded back and said my calculation was like 50% too low.

I've attached my materials list, with dimenions and my calculations. If someone can set me straight, I'd greatly appreciate it. I'm sure I did it wrong, but am not sure yet what I did wrong.

Thanks much!

[Larry Fox]

M (Mark? Mike?).

I would like to take a look at the sheet but am hesitant to open a doc file for fear of nasties lurking. It might be better to post a sample or so so we can get a sense of your calculations.

A board that is 12" wide x 12" long x 1" thick is one board foot. I use a volume calculation when I figure mine. A board foot is 144 cubic/inches. It might also be the case that there is nothing wrong with your calculations but your supplier might also be figuring in a waste factor where you are not. For some species, some suppliers have a recommended waste factor and it can be quite high. If I recall correctly cherry is somewhere near 50%.

[Jerry Strojny]

Unless I've been doing it wrong all this time, your calculations seem to be right. I always add about 10 to 20% more for cuttoffs and "bad" areas on the boards. 50% off doesn't seem to make sense to me.

[Kent Fitzgerald]

Welcome!

Your math looks fine, but the problem is that rough lumber is sold as random length and width (RWL) boards. You pay for the whole board, not just the finished dimensions that you need.

As an example, to get the 4" wide drawer parts, you'd start with a 5" or 6" rough board. You only need 64", but the shortest boards at the yard are probably at least 6'. That means the rough BF total for those parts would be more like 2.5 BF, rather than the 1.67 BF that you calculated.

[Martin Shupe]

Board feet is found by multiplying L X W X Thickness, all in inches, and then dividing by 144.

If you are making a table, you will probably need 4/4 lumber (one inch thick) and 8/4 lumber (two inches thick) for the legs.

It is almost always better to buy more lumber than you need, so that you can choose the best grain for pieces like tops and drawer fronts.

For this reason, I prefer to work in only two or three species.

[Jesse Cloud]

Hey M,
As far as it goes, your calculation is correct. There are two additional issues, though.
1)Your dealer probably doesn't have boards exactly the size you need (e.g. 10 inches wide and 20 inches long). You will probably need to buy longer and thinner boards and glue them up to get 10 inches wide. As Kevin pointed out, you will pay for the whole board.
2) The issue of waste, scrap, etc. Depending on how picky you are and how good the wood is, you may run into 50% waste, though thats a tad high. I consider anything shorter than a foot to be firewood because its dangerous to machine short pieces. And I know you would never do this, but I usually make a mistake or two in each project, so if the piece is complicated, I may make a spare leg and a spare apron just for insurance...

So, the lumber yard guy probably isn't ripping you off, but use your own judgment about how much extra you will need. Its always better to buy everything at once, rather than making a second trip to the lumberyard when you run out and hoping you can match the grain pattern and coloration of the first batch you bought.

Welcome to the creek!
Jess

[M Smith]

Thanks for your help and replies. I did try to post the materials list in my message, but I couldn't get the columns to line up, so instead of posting it unreadable in my message, I elected to attach it. No viruses!

Anyways, here is the reply I got from the wood shop:

"Your project requires NET 12.5 bdft of 4/4, the overage will bring it to about 16 bdft. For the legs, add 5 bdft."

Using his math, I would need about 21 bdft total, where I calculated 12 bdft. I knowingly did not account for overage -- but would it be THAT much?

Thanks again,
Mark

[Al Willits]

Like said, better to much than not enough, as a newbie, I'm finding that out.
Better to buy extra as that trip back to the lumber yard costs time and money, and you have to match what they have with what you have, sometimes easier said than done.

Besides you'll have a bit left over for another project maybe.. :)

Al

[Rob Russell]

Mark,

Welcome to SMC. It could definitely be as much as a third waste. If you take the time to layout the pieces you need into boards that are 8' long, you can minimize your waste.

You don't say what type of wood you're using and that can be significant factor. As an example,if you're using cherry and want only the red heartwood, you need to be prepared to slice off an inch or more from each side of a board to get to heartwood.

FYI, we use full names here, so send either an email (http://www.sawmillcreek.org/sendmessage.php?do=mailmember&u=111) or a PM (http://www.sawmillcreek.org/private.php?do=newpm&u=111) to one of the admins and they'll update your profile.

One other comment on your wood purchase - it's OK to have a little bit left over that you can use for your next project!

Rob

[Doug Shepard]

Look at it this way. A typical BF of cherry might have anywhere from 1-1.5" of sapwood on the edge, and often on both edges. For a 10" wide board, that's 10% min. waste, and maybe as much as 30% waste. That's before even worrying about length waste for cutting around defects. 50% might sound high, but it's probably not too far off.

[Rick Doyle]

Hi Mark,

Here's a Bd. Ft. calculator, in MS Excel, that you can download and use to figure out multiple boards for a project. It's simple - but, it works!

http://www.rickswoodworking.ca/tips_&_techniques.htm#Board

Rick

[Martin Shupe]

If you can find a local lumber yard that will let you pick your own boards, you will reduce your waste. I never shop for lumber unless I can pick my own boards. Of course, you must restack the stacks as a courtesy.

If you will tell us the region of the country where you live, perhaps people on this board can help you find a good place to buy lumber.

[M Smith]

Mark,

FYI, we use full names here, so send either an email (http://www.sawmillcreek.org/sendmessage.php?do=mailmember&u=111) or a PM (http://www.sawmillcreek.org/private.php?do=newpm&u=111) to one of the admins and they'll update your profile.

Rob
I tried to register using my full name, but apparently someone else got here first so it wouldn't let me use my first name. I'll ask the admins to fix that if possible.

Thanks again for all your help guys! Looks like I underestimated the material I need, but I still think the lumber yard overestimated. Hopefully I won't have 50% wast. Great insight and advice!

Mark

[M Smith]

If you can find a local lumber yard that will let you pick your own boards, you will reduce your waste. I never shop for lumber unless I can pick my own boards. Of course, you must restack the stacks as a courtesy.

If you will tell us the region of the country where you live, perhaps people on this board can help you find a good place to buy lumber.

Martin,

I'm in northern Virginia, just west of Washington, D.C. I know of a couple shops locally that have decent reputations. The place I got the bdft estimate is a new shop, so I don't know anything about them. They're just right around the corner from me.

The wood I'm considering is indeed cherry. I talked to one of the shops today and the guy told me that I could come pick my wood as he had a lot of smaller pieces of cherry. So, that may be the route to go.

Again,
Thanks

[Rob Russell]

The wood I'm considering is indeed cherry. I talked to one of the shops today and the guy told me that I could come pick my wood as he had a lot of smaller pieces of cherry. So, that may be the route to go.


Mark,

If you pick out your own cherry, be careful of pitch pockets - that's another way that cherry becomes less useable.

Rob

[Martin Shupe]

Mark,

If you pick out your own cherry, be careful of pitch pockets - that's another way that cherry becomes less useable.

Rob

Unless your wife prefers pitch pockets in her cherry. One man's trash...

I buy my cherry from a mill in Illinois; "western" cherry. It has more pitch pockets than PA cherry. My wife likes them, so I find myself choosing boards that all have pitch pockets when I make something for her. As long as there are a few in every board, the boards go together.

Another "style" of cherry I have is "mineral" cherry. It has dark, almost black stains. I try to keep that together in projects as well. I just wish I had more room to sort all the different types! I also keep an eye out for quartersawn cherry with nice ray fleck, and curly cherry, which is a little rare.

Mark, it may be worth your time to take a drive to PA sometime for cherry at Hearne Hardwoods or Groff and Groff. I think you can find both on the web. Bring a large wallet, however, as there is so much beautiful cherry you will want to buy it all.

Cherry does have a lot of variation, so if you can buy lumber from the same log ("log run"), it will be easier to match the boards for your project.

[Alan Turner]

Mark,
Welcome to SMC.

Go to the yard, and take your cut list, and a piece of chalk, and a small hand plane. Most yards will let you plane a few areas lightly to check grain and color. The waste factor on cherry can easily be 50%, depending. On mahogany, I usually figure about 20%, which is the least I ever figure.

Note that for leg stock, either 8/4 or 12/4, some yards will let you cut the length down, and take what you want, if what they are left with is saleable. For example, for a 14' board, you could sometimes buy 6', leaving them 8'.

Also a note -- for the leg stock, carefully select the stock as leg stock is best if rift sawn. That way the contiguous faces have similar grain.

[Maurice Metzger]

I'm in northern Virginia, just west of Washington, D.C. I know of a couple shops locally that have decent reputations. The place I got the bdft estimate is a new shop, so I don't know anything about them. They're just right around the corner from me.

The wood I'm considering is indeed cherry. I talked to one of the shops today and the guy told me that I could come pick my wood as he had a lot of smaller pieces of cherry. So, that may be the route to go.


Hi Mark,

Northland Forest Products in Manassas (http://www.northlandforest.com) is a good source for wood in the northern Virginia area. I stopped in there last week and they had some 4/4 quarter sawn and flat sawn cherry in short lengths (6 feet?) for sale as a special - they don't always have it. That might be an option for a small project. As others have noted, most pieces have an inch or so of sapwood that needs to be trimmed.

No connection to NFP.

HTH,
Maurice

[M Smith]

Hi Mark,

Northland Forest Products in Manassas (http://www.northlandforest.com) is a good source for wood in the northern Virginia area. I stopped in there last week and they had some 4/4 quarter sawn and flat sawn cherry in short lengths (6 feet?) for sale as a special - they don't always have it. That might be an option for a small project. As others have noted, most pieces have an inch or so of sapwood that needs to be trimmed.

No connection to NFP.

HTH,
Maurice

Maurice,

Thanks much for pointing me towards NFP. If I can break free this weekend, I'll go by and see what they have.

Regards,
Mark