certainty.
A much more difficult task has been to figure the live weight of a bear in the field using measurements. The best calculation I have found is the following (for boars only):
Weight(kg) = 7.673 + .00005891(Chest Girth(cm) x Length(cm))
For additional information on this equation and others regarding black bear weight check out a research paper called, “Interpopulation Applicability of Equations to Predict Live Weight in Black Bears” by Swenson, Kasworm, Stewart, Simmons, Aune.
The paper mentions that the equation was developed for certain bears in certain locations (MT). The gender also seems to play a large roll in the accuracy of the equation. But if you are looking for the approximate live weight of black bear boars in the field, the calculation above appears to get you close.