If you have an encounter with, say, a dozen kobolds (25 xp each) and a young white dragon (2300 xp), coming up with the actual difficulty is hard.
If you just combine them, that's 2,600 total exp, x3 for 11-14+ creatures, total 7,800. That's obviously too high.
If you follow the rule of "don't count any monsters whose challenge rating is significantly below the average of the other monsters in the group", you wind up with 2,300 xp, which is too low because surely those kobolds count for something.
If you treat them as two separate encounters, the kobolds have an adjusted xp value of 900, the dragon is 2,300, and the total is 3,200.That's looking more plausible, but they really aren't separate encounters.
So, doing a bit of math, I think I came up with a better way: the encounter multiplier is roughly the square root of the number of monsters (it's not perfect, but it's close). For fixed capability creatures, you can have the same effect from sum ( 2/3 power of the xp of individual creatures )^3/2. For example, the 2/3 power of 200 (a CR 1 monster) is 34.2, so if you have four of them, you want (34.2*4)^3/2, which is 1,600 (which is in fact the same as the DMG calculation). Obviously, that's not an interesting case, but if we apply it to our dragon and its kobold servitors we get:
each kobold: power(25, 2/3) = 8.55; 12 of them is 102.6
one dragon power (2300,2/3) = 174.2; total with kobolds is 276.8, which taken to the 3/2 power is 4606, implying that adding the kobolds makes the dragon about twice as hard.
That seems reasonably fair; if you focus fire the dragon (which has a total attack of +7/41) you have kobolds slinging you (for total attack +4/54, likely with advantage from pack tactics), if you instead mop up the kobolds the dragon is getting a couple free rounds to beat on you.
For party size, rather than changing encounter multipliers, just multiply budget by sqrt( party size/4 ); thus, a single level 1 PC only has a medium budget of 25.
This is easiest with a spreadsheet or an app of some sort; the above example would be something like:
Hell, I just adjust the stats on the fly if I need to. I have never bothered using the CR to XP system to come up with an encounter build. I just look over the monsters an consider how I can use it. If I need to mod stats I will and often times do. Using a single CR5 against a party of 12-13 levels is not an issue and is very easy to make a challenging encounter with even if it is just a flat out combat encounter. You dont even have to put much effort into it. Just bump up some numbers and can be done on the fly. Ill even make up NPC stats on the fly all the time. Why get to detailed into creating them. It also helps when a player decides to attack some random NPC simply for looking at them. I just created an encounter for my group using 5 CR7s, 1 CR11, and 1 CR12. All creatures are from the the Tome of Beasts (creatures are in general far more challenging for their CR rating then the monster manual). Players range between 12-13. I based it on what the creatures can do. Not what their CR level is. As far as rewarding XP. I just go the milestone route.
If you have an encounter with, say, a dozen kobolds (25 xp each) and a young white dragon (2300 xp), coming up with the actual difficulty is hard.
So, doing a bit of math, I think I came up with a better way: the encounter multiplier is roughly the square root of the number of monsters (it's not perfect, but it's close). For fixed capability creatures, you can have the same effect from sum ( 2/3 power of the xp of individual creatures )^3/2. For example, the 2/3 power of 200 (a CR 1 monster) is 34.2, so if you have four of them, you want (34.2*4)^3/2, which is 1,600 (which is in fact the same as the DMG calculation). Obviously, that's not an interesting case, but if we apply it to our dragon and its kobold servitors we get:
That seems reasonably fair; if you focus fire the dragon (which has a total attack of +7/41) you have kobolds slinging you (for total attack +4/54, likely with advantage from pack tactics), if you instead mop up the kobolds the dragon is getting a couple free rounds to beat on you.
For party size, rather than changing encounter multipliers, just multiply budget by sqrt( party size/4 ); thus, a single level 1 PC only has a medium budget of 25.
This is easiest with a spreadsheet or an app of some sort; the above example would be something like:
Hell, I just adjust the stats on the fly if I need to. I have never bothered using the CR to XP system to come up with an encounter build. I just look over the monsters an consider how I can use it. If I need to mod stats I will and often times do. Using a single CR5 against a party of 12-13 levels is not an issue and is very easy to make a challenging encounter with even if it is just a flat out combat encounter. You dont even have to put much effort into it. Just bump up some numbers and can be done on the fly. Ill even make up NPC stats on the fly all the time. Why get to detailed into creating them. It also helps when a player decides to attack some random NPC simply for looking at them. I just created an encounter for my group using 5 CR7s, 1 CR11, and 1 CR12. All creatures are from the the Tome of Beasts (creatures are in general far more challenging for their CR rating then the monster manual). Players range between 12-13. I based it on what the creatures can do. Not what their CR level is. As far as rewarding XP. I just go the milestone route.