# How is DBH calculated?



## conlan (Jun 14, 2009)

Is DBH calculated by the following formula: circumfrence divided by 3.1459, or is it more complicated than that?


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## ATH (Jun 14, 2009)

Almost....you missed a "1" in the thousandths place: 3.14*1*59

But, the big thing is to make sure you measure circumference in the correct spot. Generally, that is 4.5 feet off of the ground on the uphill side of the tree. Obviously not every tree is perfect, so there are rules for every situation.

And if you want to get real techincal...circumference is only accurate IF the tree is a perfect circle - which is rare. Calipers are most accurate - measure 2 points at 90 degrees away from each other.

But, the everyday answer to your question is "Yes".


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## conlan (Jun 15, 2009)

Thanks ATH, much appreciated.


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## groundsmgr (Jun 15, 2009)

Diameter at brest hieght. Get a d-tape and do it that way {foresrty supply}


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## conlan (Jun 15, 2009)

What is a d-tape and how is it used?


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## groundsmgr (Jun 15, 2009)

Diameter tape ( Forestry supply.com} You use it at the DBH { Diameter At brest Hieght} About 4.5 feet


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## 371groundie (Jun 15, 2009)

DBH is usually measured with a tool that saves you from having to calculate it such as:

a diameter tape: has a hook that will bite into the bark on the end, and increments that will read you the diameter in inches and tenths when you wrap it around the tree. some loggers tapes have diameter marks on the back. 

Calipers: directly measure the diameter, but are highly suceptable to errors on irregularly shaped trees. 

biltmore stick: usually has a log scale on one side and tree scale on the other. close one eye and hold the stick against the tree. 25" from your eye. line up the end of the stick with the edge of the tree and read the diameter where the other edge of the tree is. works best on trees 6-25 inches.


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## slowp (Jun 15, 2009)

The D-tape is the most accurate. You can get a plain old d-tape or get a Spencer (AKA Logger's tape) that has regular measuring tape stuff on one side, and a diameter tape on the other. Then you only have one tape to worry about forgetting. Be sure and keep the tape level while measuring. In steep country, if we can't fling the tape around the tree, catching it in the other hand, we find a forked stick and hold the tape in that while working it around the tree.


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## bulldoglover (Jun 15, 2009)

+1 on the D tape. Math makes my head hurt. Mine is a regular one, but you might want one with that nail or spike in it to hold it on the bark (I know, poor tree).


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