bf calculations when purchasing lumber

[Joe Close]

Question...

What is the generally accepted method measuring when calculating board feet when purchasing lumber from a local supplier?

For example, when buying 15/16 hickory. Is the 15/16" measurement used in the bf calc, or do they typically round up to 1" ?

What about the width of the board? I see that width varies from one end of a board to the other. Is rounding up the practice? to what? nearest inch, half inch?

I realize the answers actually relate to the specific seller. But I'm kind of curious what others experienced. I've purchased wood from two different local suppliers. Every time after I get home, I try to tie the bf of lumber I have to the ticket, and I can never make it tie. In some cases I'm way ahead, and in some cases the seller is coming out ahead.

I expect someone will ask how I calc bf...
bf = inch-width x foot-length / 12 * inch-thickness

[Joe Chritz]

The dealers I go to use a tape measure and measure the widths of the boards. The numbers keep going up until the whole pile is done. This is usually done by letting the tape stretch out. That number in inches is multiplied by the length in inches which is then divided by 144 for 4/4 stock.

I have never seen 15/16 boards in the rough (if they are it isn't 4/4). Almost everything like that has been skip planed, also called hit and miss. Usually there is a charge for the skip planing and the boards are still 4/4, some of it is just in the form of chips.

Ultimately a BF is 144 sq inches of lumber regardless of how it is formed.

Joe

[John Keeton]

Joe, as you acknowledge, a "board foot" is a measure of volume. So, it is based on actual measurements for the entire board. If a board were 8" on one end and 6" on the other - I would use 7" as the multiplier. I would expect the board to be at least an inch thick for calculation, but normally would not buy a very wide board that was less than 1-1/16" thick. But, I would calculate the measurement based on 1" - even though that is not technically correct.

To be technical, you are buying true volume. So, if it is still rough, a 15/16" board should have a reduction factor of 6.25% on the overall footage. Just make sure you have a use for wood that mills out to less than 3/4", because it is likely some (or most?) of the wood you buy may not plane out to 3/4".

And, most importantly, I do my own calculations on the spot. I am either satisfied with the deal when the money changes hands - or I walk away. There are many factors, other than simple footage. They cut hardwood lumber every day, and that is not the last hickory you will ever see for sale. "Getting home" and finding a variance in footage is probably not a good plan.

And, a BF is actually 144 cubic inches, not square inches.

[Wilbur Pan]

There seems to be a run on BF calculation questions recently. I posted this on the General board.

Here in New Jersey, it seems that the lumber dealers "measure up" in terms of thickness and width. So S2S 4/4 stock is really 15/16" planed, and if a board is of uneven width, they tend to charge according to the widest point of the board. But length measurements are right on, and calculations are done accordingly.

[Joe Close]

"Getting home" and finding a variance in footage is probably not a good plan.

Hi John,
I agree. I guess I'm going to have to become hard-nosed about this stuff on future trips to the warehouses. Do my own calcs, and have them explain the differences.

Thanks for the input!

[David Keller NC]

Joe - Regarding the discrepancy in board feet, how much are you talking? If the answer is in the second, or even first, decimal place for over 50 b.f. of wood, I'd suggest that you shouldn't expect that kind of accuracy. Generally, I will only complain if the dealer's b.f. measurement and mine disagree by more than 5%, and sometimes 10% if the lumber's a really good deal.

That said, though, most any lumber dealer I've ever been at charges based on the rough dimensions of the board, regardless of whether it's still rough or S2S, or S4S. Typically, a 3/4" S2S board is priced based on the 4/4 stock that it came from, sometimes with an additional milling fee added, sometimes as just an "S2S price".

Moreover, I'd expect that the lumber guys I deal with not to charge me for heavy wane/splits at the ends of a particular board if it's an expensive species or extra wide/thick. In fact, all of them that I know (I buy regularly from 4 or 5 different ones) will deduct a foot or so off the length measurement of a board with largely unusuable waste on the end.

[Mike Henderson]

Around here the suppliers do it the way David described - they use the rough dimensions to calculate bf. They'll also deduct bad ends, but only if you point it out to them. Let on their own, they'll charge you for it. The amount they deduct is subject to negotiation, so it depends on which employee is checking you out.

Take a calculator with you and do a rough estimate of the bf. If their calculations are way off from your estimate, stop and have them go over their calculations with you. Everybody makes mistakes - could be you, could be them - so they shouldn't object to checking the calculations.

My policy is that once I take the stuff out the door, the deal is over. If they overcharged me, shame on me, and I eat it.

Mike

[Joe Close]

Joe - Regarding the discrepancy in board feet, how much are you talking?

With my latest purchase, based on my calcs, even rounding 15/16 up to 4/4, I have a total of 32.13bf. Their total is 36bf. I would not be so concerned about +/- 1bf on $2.50/bf lumber. But nearly 4bf descrepency has made me wonder if there is something I'm doing wrong, or making incorrect assumptions about lumber.

Mike, I agree, once out the door, it's a done-deal. Shame on me.

[David Keller NC]

Joe - Sounds to me like a mistake was made (either your calcs or theirs). The calculations should've been closer than 10%, and you're over that. Unless it was really expensive stuff though (like ebony or cocobolo), I think I'd just eat it and watch carefully next time.

[Gary Blum]

Hi Joe,

One possible explanation for the descrepancy would be if the lumber was straight line ripped. I always have my lumber SLR one edge, but the scaling is done before it is run through the ripsaw. So if I measure the pile delivered, it will be less depending on the skill or attention of the guys running the ripsaw.

I'm sure some firms just add a percentage for this waste when sellilng retail.

Gary

[Johnny Kleso]

What they use is the size of the board before it was milled.. They use the sawn size at the check out even if its milled..

Someone has to pay for the lost wood in milling and you know who that is going to be :)

Also 4/4 boards in general are sawn 1 1/16" +

If you'er surface area (lenghts x widths) is off thats a mistake from what I know...