Every edition has a different experience requirement per level and a different amount of experience gained per monster killed. However, these are just numbers and don’t really have much significance individually. What players are really concerned with is how many monsters do they have to kill to gain a level.
4e had an interesting approach, tying together the two tables referred to above in such a way that every ten “balanced” encounters would yield exactly enough experience to gain a level.
5e dropped that approach. Until now, I hadn’t looked very closely at what they actually had done. All I knew on the matter was that there was some grumbling on the forums about how the experience tables allowed players to zoom past the first few levels and then gains got much harder from there. I never examined these claims until now. After taking a look, I must say that I am a bit surprised by what they’ve done.
Extracting the Data
On page 9 of the 5e Monster Manual, CR is defined as follows:
An appropriately equipped and well-rested party of four adventurers should be able to defeat a monster, that has a challenge rating equal to its level, without suffering any deaths.
This is followed by a table listing the amount of experience the party gains for defeating a monster with the listed CR.
On page 15 of the 5e Player’s Handbook, there is a table listing the experience required to attain each new level.
Calculating Encounters Per Level
To determine the number of encounters needed to gain a level, we will assume that each encounter consists of four adventurers, all of the same level, and a single monster whose CR is equal to the level of the party members. Further, each party member will receive an equal share of the experience.
From the first table, we are only concerned with CR 1 through 19 (Since a character cannot attain a level beyond level 20, we aren’t concerned with experience gained from further encounters). The experience listed on this table is for the encounter. Since there are four adventurers, we will divide this amount by four to determine how much experience each party member receives from the encounter.
The second table lists the amount of experience needed to attain the corresponding level. This is a cumulative amount, so to gain a level we need the amount of experience to attain the next level minus the amount needed to gain the current level. This will give the experience needed to move between levels, instead of the total experience to reach a given level.
Then it is a simple matter of dividing the amount of experience needed to gain a level (Goal) by the amount of experience gained from killing a monster with the corresponding CR (Exp/Person/Enc). This is all shown in the following table.
Below is a chart based on that data, showing the number of encounters required to gain each level (based on the last column from the table above).
As you can see, it is a rather bizarre progression with no logical rhyme or reason. It does support the comments on various forums that characters move quickly through the first few levels and then slow down significantly. However, progression then speeds up considerably but bounces around from there on out.
I have no idea what the designers could have been thinking here. Most likely, they weren’t. I think it is more likely that the two tables (exp needed to level and exp by cr) were constructed rather arbitrarily and no one bothered to see what impact the two tables had on encounters per level. I have to say, I’m a bit disappointed in the lack of attention to detail shown here in not producing a more logical progression. It works, but it is sloppy.
I do think it is interesting that, on average, it requires roughly 10 (10.64) encounters to progress from one level to the next. It is similar to what was used in 4e, but I suspect that is purely coincidental.
Note that all of this is just to determine a good rule of thumb. It is entirely based on “balanced” encounters, as defined by CR (listed above).
Anyone who has been here for long knows that I am not a fan of balanced encounters. Or, more precisely, I do not think that players should expect that every encounter has been balanced just for them. Some encounters are easy, while others should require that you leave the area by the fastest route available.