Rounding Numbers when Figuring Board Feet
The correct practice is to round up or down to the closest whole number. October 4, 2007
Question
Although I know the basics of measuring the amount of board feet in a board, I would like to know what to do when the measure falls between even numbers. For instance, 4.5 feet. Do you round up to 5 or round down to 4? I have bought much lumber over the years from two different suppliers and the number of board feet has always been written on the end of the board in crayon. Always a whole number, never a fraction. I want to make sure I don't advertise more of my own lumber than I actually have, and also don't want to cheat myself out of any board footage.
Forum Responses
(Sawing and Drying Forum)
From contributor Y:
At my lumber yard they round up at .5 or higher to get to a whole number.
From Professor Gene Wengert, forum technical advisor:
For hardwood lumber, the answer is always given to the closest BF. This means rounding up or down to the closest whole number as appropriate. When the answer is exactly on the half BF (that is, at x.50 BF), then the instructions are to go up the first time, down the next, up the next, then down, etc. It is incorrect to always go up; the rules are clear. Note that softwood lumber is reported to x.xx.
From contributor D:
I see that Gene answered your question, but you could Google "Illustrated Grading Guide" and download the PDF file for an extensive explanation on NHLA grading and measuring rules. It is not the complete set of rules but it should answer most questions you would have. It is very informative with lots of pictures of different grades and species.
From the original questioner:
Thanks for the information. The above website has great illustrations. I will print it and keep it with my sawmill information.
From contributor P:
The way we round numbers in engineering is:
Less than 0.5 you go down to the next lowest whole number
Greater than 0.5, you go up to the next whole number.
Exactly equal to 0.5, you go whichever way makes the number even, i.e.
6.5 rounds down to 6
7.5 rounds up to 8
