Regan C. said: I would not know where to put this so I will put it here. Exp calculators overstate the difficulty on most encounters usually. First I'll explain why this happens, and then how you can fix this.
The biggest culprit for easy encounters is the party resting
too much. If you're like me, your parties tend to have maybe two or
three encounters per long rest, often with short rests in between - this
makes more sense for some play styles, but causes balance problems.
The 5th Edition system assumes that parties will have at least a
couple of encounters between each short rest, and maybe two or three
short rests between each long rest. This forces characters to be much
more conservative with their limited resources (spell slots, class
features, hit dice, and so forth), making each individual encounter
tougher. A party that can approach an encounter fresh, with no worries
about saving resources, will often find that encounter relatively easy.
How do you fix this? You have two choices.
Don't let your party rest as often. There
are a couple of ways of doing this - you could have encounters happen
closer together without any chance for a break between each (maybe
putting the characters on a timer, or make it dangerous to rest), or use
the "Gritty Realism" rest model as described in the DMG (page 267)
which makes rests take longer.
Make the encounters harder. You can
probably make the Adjusted Difficulty Rating of an encounter double or
maybe even triple (for experienced parties) the XP rating of a Deadly
encounter, and the fight will be more challenging and risky, but not
impossible for a prepared party. This is a lot harder to get right and
you may need to increase the difficulty slowly until you get to the
level of challenge you want.
Especially don't let your party rest in a dangerous location. Coffee breaks don't make sense in the middle of dungeon, just saying.