Board Feet on the Incorrectnet

Good grief.

I’m planning a workbench project to replace the workbench-shaped object that graces my shop.  It’s crooked, too light and has vises that don’t vise.  And it’s a topic for another day.

Jackel Enterprises has a sale on currently, $2.50 per board foot for recycled Douglas Fir timbers.  Here is my line of thinking: “Maybe I should pick up enough to make a benchtop, it would be good practice with my hand planes and shouldn’t be too much money.”

Being lazy I googled “board foot calculators”.  Top of the list is the Board Foot Calculator from the University of Missouri.  I plug in 4″ thick by 18″ wide by 96″ long, and $2.50 per board foot.  OK, I need 576 board feel and $1,440.  WHAT?  If you navigate up a level from that page you’ll see that they have a very nice page on the Measurements and Pricing of Primary Wood Materials where they explain that board feet are calculated as (length * width * thickness) / 12.  Not likely.

The third entry on the google results page is another calculator from Sawdust and Shavings.  They explain, correctly, that board feet is a volumetric measure.  One board foot = 144 cubic inches.  They even give the correct formula, then proceeds to calculate it incorrectly.

So the top two sites as ranked by google provide the wrong answer.  Must be the new math.

In truth there are 48 board feet of lumber in the finished bench top (18″ x 4″ x 96″), and I’ll probably shorten it to just 6′.  Would it be wrong to buy myself an early Christmas present?

Categories: Uncategorized | Tags: , , | 4 Comments

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4 thoughts on “Board Feet on the Incorrectnet

  1. J. Pierce

    You would have gotten the proper answer on the first calculator if you had noticed that the last entry was for *feet* and not *inches*. I’ve made that same mistake when using that calculator and been left scratching my head. This gives you the 12 instead of 144 in the calculation, because you’ve already gone with feet for the length measurement.

    Interestingly enough, the second link, which gives you the formula divided by 144, which you would use if all three of your measurements are in inches (although it’s frustrating to see a formula listed without units!) still specifies “feet” for the length input field. So once again – the number you got was right – if you wanted 96 feet and not 96 inches of length. And their formula won’t work if you do it by hand and punch feet into the “divide by 144” formula. (You end up with an easy-on-the-wallet 4 board feet!)

    Either way, good luck on the bench! I’m in the middle of finishing mine, and even having a glued up heavy top on sawbenches makes everything so much easier! Be glad you went with the DF – I’ve done all that same planing in maple – no fun!

    • In the immortal words of Homer Simpson, DOH!

      I’m sure glad this isn’t “McGlynn on Math”. At work we call that operator error.

  2. Have you found Marc Spagnuolo’s board foot calculator, etc? Link -> http://thewoodwhisperer.com/the-woodshop-widget/. Watch out, his site has the potential to consume hours.

    • I frequent Marc’s site, although I haven’t seen his calculator until you pointed it out. I did discover some interesting math facts, like UNITS, by writing this post. McGlynn on Math indeed.

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