title_body: Aeropress: does filling it full with water increase the caffeine content of my cup?
upvoted_answer: Of course, I assume that the same amount of coffee is used for both cups.
  
  In that case:
  No
  Caffeine dissolves very readily in water. The caffeine content in your cup is mainly and almost solely determined by the amount of coffee you use. The impact of any other factors such as amount of water, water temperature, and pressure are negligible.
  To get a rough estimate of the amount of caffeine in your cup do this: multiply the amount of coffee in grams by 10, that's roughly the amount of caffeine in milligrams.