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.