# How to estimate is the branch thick enough to stand on it?

Some geocaches are placed high on trees:

You need to climb there to log. But standing on too thin branch can be very dangerous.

Is there a formula to estimate how thick must be a branch of a given species of tree to hold the weight of man? Of course we are talking about solid, healthy (and not rotten branches).

For example, how thick should be an oak branch to hold a weight of 70kg man?

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None that I know of. But then, I've only climbed one tree till date ;) – Unsung Jan 24 '14 at 7:28
Great question, but I don't know if you'll get a well qualified answer here. I suggest asking professional arborists. Of course they should also be connected with a rope, but they should at least have experience with what does and does not hold weight, be able to recognize a rotten branch, etc. – Mr.Wizard Jan 24 '14 at 9:12
As the comment mentioned below, it's more about where you step. I have successfully climbed trees smaller than some of the limbs in your picture, on 1" branches, by putting my foot right against the trunk. – Russell Steen Jan 28 '14 at 15:24

I don't think `estimating` is the correct approach to climbing trees.

See, from mechanics, the tree branch is a cantilever beam. So comparing branches could be done if stepping only at the base of it, only with one foot.

Then there is the variable is the branch live or dried out.

Lastly, calculating the strength of a branch would include not only successfully identifying the type of tree, but will also be very sensitive to the diameter of the branch. Are you going to be carrying sub-mm accuracy callipers and measure each branch?

Having said that, my approach to climbing trees is as follows:

• Follow the 3-point principle. At any moment of time, have three points of stable attachment to the tree. If you slip or a branch breaks, you should NOT fall, but hang on the remaining two.

• Look out for dry branches. Be very sceptical towards their strength.

• If in doubt, test the branch. With a leg or hand, push the branch downward about half a meter from the base. Get a feel for how much it bends. If it looks safe, step at it's base, right next to the three trunk.

• Look back often. It is no fun to discover that you have reached your goal ... and now can't climb down safely.

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Stepping on dry branches is possible, but only after (1) giving it a nice kick to test it and (2) stepping right next to the trunk of the tree and (3) still not trusting it, being ready to relay only on the other contact points e.g. hand grip. – Vorac Jan 24 '14 at 14:34
Nice tip that you should place your leg as near the base as possible :) – Danubian Sailor Jan 24 '14 at 17:09
@ŁukaszL., yea, one can step on pretty darn thin branches like this, provided the above safety points are observed. In the end the struggle goes from "how do I not fall to my death" to "how do I not brake any branches on this lovely tree." – Vorac Jan 26 '14 at 8:30