This paper examines and evaluates the range of methods that have been used to make quantified claims about the likelihood of Existential Hazards. In doing so, it draws on a comprehensive literature review of such claims that we present in an appendix. The paper uses an informal evaluative framework to consider the relative merits of these methods regarding their rigour, ability to handle uncertainty, accessibility for researchers with limited resources and utility for communication and policy purposes. We conclude that while there is no uniquely best way to quantify Existential Risk, different methods have their own merits and challenges, suggesting that some may be more suited to particular purposes than others. More importantly, however, we find that, in many cases, claims based on poor implementations of each method are still frequently invoked by the Existential Risk community, despite the existence of better ones. We call for a more critical approach to methodology and the use of quantified claims by people aiming to contribute research to the management of Existential Risk, and argue that a greater awareness of the diverse methods available to these researchers should form an important part of this.