How many lemons does it take to squeeze 1 cup of juice?

Excuse me, could you please elaborate on the process of juicing lemons? Specifically, I'm curious to know - how many lemons are typically required to produce a full cup of lemon juice? Is there a standard ratio or does it vary depending on the size and ripeness of the lemons? Also, are there any techniques or tips that one should keep in mind while squeezing the lemons to ensure maximum juice yield? I'm quite intrigued by this and would love to hear your insights.