Did you ever pay attention to the “suggested group size” for raids? 5 for a Metapod, 9 for a Sandslash, 13 for a Machamp and 20 for a legendary.

Of course it doesn’t make sense.

Here I propose a (simple?) formula to calculate a much more realistic “suggested group size”.

Since there are different views on this topic, I provide three slightly different versions of the formula, only with different coefficients.

Hardcore players with extremely optimized attackers:

Minimum Group Size = ceiling [Defense x HP / Time / 3400] – 29% if double vulnerability

Typical L30+ players in a “regular” raid group with good L30 attackers:

Realistic Group Size = ceiling [Defense x HP / Time / 1700] – 15% if double vulnerability

Casual L20+ players who can do a Google search or ask more experienced players and just avoid basic mistakes like using Gyarados against Raikou:

Casual Group Size = ceiling [Defense x HP / Time / 1133] – 15% if double vulnerability

Defense x HP is just the raid boss’s tankiness.

Divided by time, it’s the needed DPS (Damage Per Second) to defeat the boss.

The coefficient is 3400 for the minimum group size (found heuristically as the best match with Pokébattler simulations), then the group size is doubled for “regular players” (so 1700) and tripled for “casual players” (so 1133).

In case of double vulnerability, deduct 29% (i.e. full type effectiveness bonus) in case of “hardcore” minimum-group/solo raid, while only 15% (i.e. half of that) in case of “regular” or “casual” raid, because not everyone will have a full team of optimal doubly Super-Effective counters.

So here is the table for current raid bosses + Ho-Oh, sorted by increasing difficulty (which is just the “Realistic Group Size” with 1700 coefficient before the ceiling operation):

	Raid Boss	Base DEF	HP	Vulnerability	Difficulty (unrounded)	Minimum Group Size	Realistic Group Size	Casual Group Size
	Metapod	94	600	single	0.2	1	1	1
	Charmeleon	129	600	single	0.3	1	1	1
	Ivysaur	151	600	single	0.3	1	1	1
	Wartortle	155	600	single	0.3	1	1	1
	Sableye	141	1800	single	0.8	1	1	2
	Magneton	182	1800	DOUBLE	0.9	1	1	2
	Marowak	200	1800	single	1.2	1	2	2
	Sandslash	202	1800	single	1.2	1	2	2
	Porygon	139	3000	single	1.4	1	2	3
	Tentacruel	237	1800	single	1.4	1	2	3
	Scyther	170	3000	DOUBLE	1.4	1	2	3
	Gengar	156	3000	single	1.6	1	2	3
	Machamp	162	3000	single	1.6	1	2	3
	Omastar	227	3000	DOUBLE	1.9	1	2	3
	Cloyster	323	1800	single	1.9	1	2	3
	Alakazam	194	3000	single	1.9	1	2	3
	Ninetales	204	3000	single	2.0	2	3	4
	Victreebel	138	7500	single	3.5	2	4	6
	Nidoking	157	7500	single	3.9	2	4	6
	Nidoqueen	174	7500	single	4.4	3	5	7
	Entei	180	12500	single	4.5	3	5	7
	Lapras	180	7500	single	4.5	3	5	7
	Tyranitar	212	7500	DOUBLE	4.5	2	5	7
	Mewtwo	182	12500	single	4.5	3	5	7
	Poliwrath	187	7500	single	4.7	3	5	8
	Snorlax	190	7500	single	4.8	3	5	8
	Golem	229	7500	DOUBLE	4.9	3	5	8
	Raikou	210	12500	single	5.2	3	6	8
	Ho-Oh	274	12500	DOUBLE	5.8	3	6	9
	Suicune	235	12500	single	5.8	3	6	9

An interactive calculator, also with legacy species, Mythical Pokémon and a field to calculate it for an arbitrary species / raid tier, is available as a spreadsheet.