In my 3rd ed book, there is a table of CR against the number of monsters a party can fight based on their level. In 5e I cannot find this table. There is some mention of encounters being based on the total exp of the stuff they are fighting but it is just a couple of sentences. However this would make the CR stat in the MM redundant.
Can I re-use the table from 3rd ed or is there a new formula for using the CR in 5e? Or am I missing something completely?
Also, what is the range of CR that they can fight, for example, if the party are found to be able to kill a monster of CR 5 by whatever calculations are used, can they kill a monster of CR 6 or 7 with great difficulty? I seem to recall 3rd ed said you'd expend a certain percentage of resources but I cannot find this in the DMG for 5th edition.
Edit: Page 82 of the Dungeon Master's Guide talks about designing an encounter, but it says nothing about CR, it only talks about creating encounters based on experience.
Best Answer
The sidebar on DMG 82 explains one important aspect of CR: a monster of higher CR than the party's average level is likely to have special features or damage output that is too much for the party to handle.
A monster's CR is equivalent to its XP reward, which is used to build encounters. As MM 9 says, one monster of CR equal to the party's level is a moderate challenge for a party of four characters. If you compare the table on MM 9 to the table on DMG 82, you can see that this is roughly consistent with the encounter building rules.
The DMG does not provide the sort of easy, shortcut rules of thumb that the 4e DMG provides for tossing together an encounter just by eyeballing the CR of the monsters involved. I find the Kobold Fight Club tool invaluable for generating encounters in my campaign.