The answer to this really depends on what you are thinking of as judgment.
If you are speaking about the sensation that is experienced as a result of an intentional act of thought, word or deed, then you are the judge (before the fact). As you intend to create experience of pleasure, you will experience pleasure; as you intend to create experience of pain, you will experience pain; as you intend to end kamma, you will experience neither pain nor pleasure.
If you are speaking about the intensity of such experiences of sensations resulting from your own actions, then, I suggest that this too is a matter judged by yourself, but yourself at the highest perspective - that will be, from the Buddhist point of view, the view closest to the Four Truths, or, stated another way, it will depend on your degree of detachment - in your experience. Here you will find that a change in perspective also has the power to change the experience. So you not only judge, but you are in control of the sentence. The danger here, and you did not ask about the danger of judging, is that the further the foundation of your view is from the highest, the harsher will be your own judgment of yourself. The fully developed compassionate heart is very forgiving.
If you are speaking about the material manifestation, the 'form', (e.g., an eye for an eye, a tooth for a tooth) that results from your intentionally created pleasure or pain or experience without pleasure or pain, then this is something that is beyond the scope of most people to determine. I have a theory that it is the collective wisdom of all beings since the beginning of time, but that is just my view.
For a warning concerning attempting to judge such matters before you have experienced the full maturity of awakening. One of the 'fruits' of arahantship is this ability.