According to Doctrine 3, Epicurus held that the limit of quantity of pleasure is the absence of pain. This is a function of the truism / premise that there are only two feelings - pleasure and pain - which means that in quantity, the measurement that describes the "absence" of the one is the same measurement as the "presence" of the other. But this observation is limited to quantity - it has nothing to do with the quality or the detail of the type of pleasure (or pain) that is being experienced at a particular moment.
Nevertheless, there is at loose in philosophical communities today the idea that Epicurus taught that pleasure is exactly equal - is defined as - "absence of pain," and so many are motivated to try to reconcile the inconsistencies in the texts by holding that Epicurus meant "tranquility" and that "tranquility itself" is the goal of life. What they would really say, if they followed their conclusion to the end, is that "tranquility is the highest pleasure" -- but you rarely see that formulation, as it is so obviously and counter intuitively incorrect.
The record of how all this discussion got started is out there if people would look. Much of the story begins with Plato and Philebus, but Epicurus was not the only one to grapple with the issue. One philosopher -Heronymous of Rhodes - explicitly adopted the modern "absence of pain" position - and everyone at the time knew the difference. Heronymous of Rhodes is forgotten today, but Epicurus is tagged with his incorrect viewpoint. Beware!
Cicero - Academic Questions:
Cicero - On Ends:
I will give Hieronymous credit for one thing: he is consistent in seeing that holding up "absence of pain" as the goal means to depreciate "pleasure" as the goal of life. Whether they admit it or not, this is the natural road which proponents of "absence of pain" will follow - they end up being opponents of "pleasure" as ordinarily understood.
Next - again from Cicero, On Ends:
Cicero the lying litigator at work again! Cicero KNOWS that Epicurus did not make the mistake of calling "absence of pain" the goal of life, as Hieronymus did, but because some are so obtuse as to think "absence of pain" makes sense (Hieronymous was such a one!) Cicero is able to use the argument to great effect - or so he thinks! But once we see that the goal is PLEASURE, rather than absence of pain, Cicero's argument falls to the ground: