Cubic feet calculations

[russ_1380]

Hi everyone and happy New Year.

Just a quick question:

I appreciate the traditional measurement of timber is in cubic feet.

When ringing suppliers, I find some give a price for a cubic foot of a certain profile of timber (e.g 1 x 6 inch etc). This is fine and I appreciate the fact that wider boards will cost proportionally more than skinnier boards hence the difference in cubic foot price.

What I don't understand is best described with a theoretical example:

---Oak £55.38 / cubic foot (in 2 x 6 inch planks)---

When I calculate this I work out that for my cubic foot of timber, I should be given a length of timber approximately 144 inches long. (2 x 6 x 144 = 1728 or the volume of 1 cubic foot.)

The planks they have offered me have been far shorter than this.

The timber shops will know what thy are doing far more than me, so am I doing something fundamentally wrong here with the figures and my calculations?

Thanks

Russ

 

[wysong]

You buy your lumber by the CUBIC foot .
how strange , that sounds over here

Over here it's bought/sold by the board foot

1" T by 12" W by 12" L = 1 BF

then it's 4/4 , 5/4 6/4 8/4,12/4 and so on for thicknesses

 

[kirkpoore1]

You buy your lumber by the CUBIC foot .
how strange , that sounds over here

Over here it's bought/sold by the board foot

1" T by 12" W by 12" L = 1 BF

then it's 4/4 , 5/4 6/4 8/4,12/4 and so on for thicknesses

And to expand on what Hutch is saying, a 2 x 6 isn't 2" x 6"--it's 1-1/2" x 5-1/2", while the "quarter" designations are final dimensions--four quarter (4/4) is 1", 5/4 is 1-1/4", etc. But that's the US/Canadian convention--I don't know what you're facing there.

Kirk

 

[Scrums]

Hey guys from across the pond....you want to hear some really wierd stuff...?

We normally buy our softwood(that's Pine to you) in ie: 6" x 2" x 2.4metres/3.6/4.8metres and so on

But back to Russ's question - hopefully you're talking PAR here?....you need to establish with the mill/supplier whether you're getting 6 x 2 before finishing or you want that as a finished size, I think the assumption is that it starts at 6 x 2 before machining and that's what you pay for. As for length - there shouldn't be any wastage on length and I'd expect to get very close to 144" or want to know why.

Hopefully £55.86 is a hypothetical price, it seems a bit on the adventurous side, the last lot of 55mm I had in - kd w/edge was approx £30 inc'vat delivered.

Cheers,

Chris

 

[9fingers]

The way I think of cu measure for timber is as follows

Imagine a hollow cube with open sides sitting on the bench measuring 12" on side. using your 6x2 example

You can get a stack of 6 no 2" boards vertically inside and you could get 2 no 6" boards across the width so 6 times 2 =12 so 12 foot of 6x2 = 1 cubic foot.

Now trying again with less confusing dimensions:-

How much 4 x 1 in a cubic foot?

You can get a stack of 12 inside vertically and 3 in a row horizontally so answer is 3 x12 = 36 foot.

Works just as well with metric but the numbers are bigger a cu mtr of wood is a lot!

How much 200 x 50 in a cu mtr?

20 in a stack vertically and 5 side by side horizontally. So 5 x 20 = 100. answer 100 metres of 200 x 50 = 1 Cu mtr.

Bob

 

[Guggs]

There is 35.315 sq inches per cubic metre
It may even be 35.351 not sure ! Ha ha

 

[Johnboy]

There is 35.315 sq inches per cubic metre
It may even be 35.351 not sure ! Ha ha

Must try harder, 1/10 for trying though.

There are 35.315 cubic feet/cubic metre or 61023.744 cubic inches.

John

 

[tomatwark]

I always order my timber in cubic feet as I can picture it in my mind as a board which is 144" long 12" wide and 1" thick.

I normally turn all my finished section sizes into cubic inches and then divide the total by 144 and then 12 this will give me the total cubic feet. I then add 25% on if I am buying straight line edged boards or 35% if I am buying waney edge boards, this will allow for machining wastage, you should have a bit left at the end of the job to go towards making something else on correct mistakes ( yes we ALL make them)

I would expect my supplier to be a small amount over the quantity I ordered to allow for the varying sizes of the boards, but if I thought they were over by too much I would send the excess back.

Tom

 

[Steve Maskery]

I think the point here is that although prices are quoted PER cubic foot, it doesn't mean there is a cubic foot in any particular board.
The reason the thickness is stated is that thicker boards require more seasoning (i.e. more energy and more time invested) so cost more than thinner stuff for the same amount of timber volume overall.
S

 

[russ_1380]

Cheers guys. And yes it was a theoretical price but i did see a similar price on a website (must have been for PAR maybe) I thought it seemed a bit dear! Plus I did mean rough sawn.

I've since rang a few timber suppliers and asked for some help explaining the situation. Basically what you have all said is correct. It was me being a bit dopey

-Thicker boards are dearer due to scarcety etc.
-My calculations were right in theory but in practice, what most timber suppliers were saying is they round it up or down to the length of the board they have. ie. they may give you slightly less than a cubic foot if it meant a true cubic foot required nibbling a few inches off a new board. Fair enough I suppose.

The main problem I had was trying to visualise what a cubic foot would look like if it were stretched in to a plank.

Buying soft wood is much easier! It seems its similar to what you mentioned, just state the profile and lenght you want

 

[wem]

I'm bumping this thread as I am getting some strange quotes from suppliers ans I cant figure out where the excess cost suddenly comes from? I'm after 14' x 5"x 1" could someone please tell me how many cubic feet this is?

 

[Chrispy]

0.486 cubic feet

 

[Steve Maskery]

Correct. What's the problem?
S

 

[RogerS]

Regardless of whether you are quoting or being quoted in cu ft or cu m, unless you tell them that you want a specific length/width/thickness then they will give you whatever they have.

So you must tell them what you want to get out of the timber supplied by them. You probably will have to take a hit on extra lengths.....for example, if you wanted 2.2m then they will probably supply you with a length 2.4m

With regard to pricing and cu ft vs cu m, it's very easy to knock up a little spreadsheet that lets you enter dimensions and/or price. For example, if you see something off eBay that you like the look of, you could enter the dimensions and the price and the spreadsheet will then tell you what the equivalent price is per cu ft or cu m so you can then compare with other timber yards etc.