This .pdf document details the Bite Scale for Dogs.  This bite scale is intended for wounds inflicted on a person by a dog, not for wounds inflicted by one dog to another dog.  This scale goes hand in hand with the "Bite Scale Perspective", so be sure to download that .pdf as well.
 
The Bite Scale was developed by Dr. Ian Dunbar as a tool for objectively assessing the severity of dog bites, because dog bites can be scary and emotional events and the descriptions provided by victims and witnesses can vary dramatically.
 
The Bite Scale removes as much subjectivity as possible by looking at quantifiable aspects of the physical wound that results from the bite.
 
The Bite Scale is such a valuable tool because dog bite incidents can be so scary and so subjective. It's essential that you can tell the difference between behavior that is scary and totally inappropriate, but ultimately safe and resolvable; as opposed to behavior that is truly dangerous and in need of immediate professional help and strict safety management.
 
A dog’s previous behavior is the best predictor of future behavior. Dogs that have inflicted a serious bite may do so again and should be managed accordingly.
 
Understanding the severity of a dogs bite is very important and this Bite Scale and the companion BIte Scale Perspective will allow you to be able to better understand the prognosis for a dog that has bitten.