How do I know my mask size?

As a frequent traveler and wearer of protective masks, I often find myself wondering, 'How do I know my mask size?' It's a crucial question for ensuring a proper fit that can optimize comfort, reduce the risk of fogging up glasses, and most importantly, maximize the mask's effectiveness in preventing the spread of airborne particles. With so many mask types and sizes available, from surgical masks to N95 respirators, it's important to understand the various ways to measure and determine the best fit for your face. Could you elaborate on the different methods one could employ to accurately determine their mask size, ensuring both comfort and safety?