Every number on this page is arithmetic you can check: Torchline budgets 4,000 XP per character at level 17 for a standard fight, scales it by party size, then by the difficulty band. Below each table are the SRD 5.1 creatures that actually land in that budget.
Budgets by party size and difficulty
Difficulty
Party of 3
Party of 4
Party of 5
Party of 6
Skirmish — resources barely dented
6,600
8,800
11,000
13,200
Standard — a real fight, rarely lethal
12,000
16,000
20,000
24,000
Hard — someone will probably go down
19,200
25,600
32,000
38,400
Brutal — a character can die here
28,800
38,400
48,000
57,600
These are effective-XP budgets: a group of monsters is multiplied up before it is compared against them, so a budget of 16,000 does not mean 16,000 XP of monsters.
What actually fits, for a party of four
The crowd multiplier is the part that catches people out. Two creatures count for 1.5× their XP, three to six count double, seven to ten count 2.5×, eleven or more count triple. So the XP you can spend per creature falls fast as the group grows.
Skirmish — budget 8,800
A lone threat — about 8,800 XP each (×1 crowd multiplier)
Creature
Type
Size
CR
AC
HP
XP
Archmage
Humanoid
Medium
12
12
99
8,400
Erinyes
Fiend
Medium
12
18
153
8,400
Adult Brass Dragon
Dragon
Huge
13
18
172
10,000
Adult White Dragon
Dragon
Huge
13
18
200
10,000
Nalfeshnee
Fiend
Large
13
18
184
10,000
A pair — about 2,933 XP each (×1.5 crowd multiplier)
Creature
Type
Size
CR
AC
HP
XP
Giant Ape
Beast
Huge
7
12
157
2,900
Oni
Giant
Large
7
16
110
2,900
Shield Guardian
Construct
Large
7
17
142
2,900
Stone Giant
Giant
Huge
7
17
126
2,900
Young Black Dragon
Dragon
Large
7
18
127
2,900
A group of four — about 1,100 XP each (×2 crowd multiplier)
Creature
Type
Size
CR
AC
HP
XP
Black Pudding
Ooze
Large
4
7
85
1,100
Chuul
Aberration
Large
4
16
93
1,100
Couatl
Celestial
Medium
4
19
97
1,100
Elephant
Beast
Huge
4
12
76
1,100
Ettin
Giant
Large
4
12
85
1,100
A swarm of eight — about 440 XP each (×2.5 crowd multiplier)