To find what level toons you can group with, choose your level on the left side.
In the green is the range you can group with.
The first (lower) number is the lowest level that can group with you to and that toon still get experience.
The second (higher) number is the highest level you can group with and you still get experience with.

1	1	2
2	1			4
3		2			5
4		2					7
5			3					8
6				4						10
7				4							11
8					5								13
9						6								14
10						6										16
11							7										17
12								8											19
13								8												20
14									9													22
15										10													23
16										10															25
17											11															26
18												12																28
19												12																	29
20													13																		31
21														14																		32
22														14																				34
23															15																				35
24																16																					37
25																16																						38
26																	17																							40
27																		18																							41
28																		18																									43
29																			19																									44
30																				20																										46
31																				20																											47
32																					21																												49
33																						22																												50
34																						22																														52
35																							23																														53
36																								24																															55
37																								24																																56
38																									25																																	58
39																										26																																	59
40																										26																																			61
41																											27																																			62
42																												28																																				64
43																												28																																					65
44																													29																																						67
45																														30																																						68
46																														30																																								70
47																															31																																								71
48																																32																																									73
49																																32																																										74
50																																	33																																											76
51																																		34																																											77
52																																		34																																													79
53																																			35																																													80
54																																				36																																														82
55																																				36																																															83
56																																					37																																																85
57																																						38																																															85
58																																						38																																															85
59																																							39																																														85
60																																								40																																													85
61																																								40																																													85
62																																									41																																												85
63																																										42																																											85
64																																										42																																											85
65																																											43																																										85
66																																												44																																									85
67																																												44																																									85
68																																													45																																								85
69																																														46																																							85
70																																														46																																							85
71																																															47																																						85
72																																																48																																					85
73																																																48																																					85
74																																																	49																																				85
75																																																		50																																			85
76																																																		50																																			85
77																																																			51																																		85
78																																																				52																																	85
79																																																				52																																	85
80																																																					53																																85
81																																																						54																															85
82																																																						54																															85
83																																																							55																														85
84																																																								56																													85
85																																																								56																													85