Group size estimator

How many trainers do I need to invite?

The Estimator is already "trainers of this attacker needed to finish inside the timer", so this page does not invent a number: it reads it off the boss's own ranked counter list for three realistic parties and re-simulates each of them at every level from 20 to 50.

Raid bossTierIVsWeatherFriendshipDodgingShadow attackersMega attackersLegendary attackers

Invite 6 to be safe — 5 if everyone is prepared

At level 40, a party of Rotom (Fan)'s top six counters needs 4.04 trainers (round up: 5), and a mixed lobby of ranks 13-24 needs 5.13 (round up: 6). The raid timer is 300 seconds and one prepared trainer alone would take 18:36. No level in this range makes it soloable with a prepared party.

Rotom (Fan) · Elite

electricflying

Weak to

rockice

Boss CP: 47,376
Boss HP: 20,000
Raid timer: 300s
Party used: 6

Trainers needed, by attacker level

Scroll sideways for the mixed-lobby column.

Trainers needed to beat Rotom (Fan) at each attacker level
Attacker level	Six of the best counter	A prepared party	A mixed local group	Prepared solo time	Faints per timer
Level 20	5(4.67)	6(5.98)	8(7.68)	27:32	6.0
Level 25	4(3.98)	6(5.03)	7(6.45)	23:08	6.0
Level 30	4(3.57)	5(4.44)	6(5.73)	20:26	6.0
Level 35	4(3.36)	5(4.24)	6(5.43)	19:31	6.0
Level 40	4(3.26)	5(4.04)	6(5.13)	18:36	5.9
Level 45	4(3.10)	4(3.91)	5(4.95)	18:01	5.9
Level 50	4(3.00)	4(3.79)	5(4.76)	17:27	5.9

Whole trainers in bold, the raw estimator in brackets — 2.04 means two trainers is right on the line and three is comfortable.

Six of the best counter

Every trainer brings six copies of the single best counter — the theoretical floor.

4 trainers at level 40

Kyurem (White)3.26

A prepared party

Each trainer brings the boss's top six counters, powered up and correctly TM'd.

5 trainers at level 40

Kyurem (White)3.26
Kyurem (Black)3.53
Eternatus4.22
Rampardos4.35
Glimmora4.37
Rhyperior4.54

A mixed local group

Ranks 13-24: reasonable but unoptimised parties, which is what a public lobby usually is.

6 trainers at level 40

Terrakion4.79
Regigigas4.79
Galarian Darmanitan (Standard)4.83
Tyranitar4.98
Weavile5.06
Glaceon5.06

The party these numbers assume

1. Kyurem (White)

Ice Fang + Ice Burn

2. Kyurem (Black)

Dragon Tail + Freeze Shock

3. Eternatus

Dragon Tail + Dynamax Cannon

4. Rampardos

Smack Down + Rock Slide

5. Glimmora

Rock Throw + Meteor Beam

6. Rhyperior

Smack Down + Rock Wrecker

See the full ranked counter list for Rotom (Fan) · check a real lobby (win chance, who brings what) · make a share card of the top six

How this is worked out

The boss is ranked once at level 40 with rankCached (the same memoised call /raids makes), then the three bands — rank 1, ranks 1-6, ranks 13-24 — are re-simulated at each attacker level with an 8-run Monte Carlo each. Holding the party fixed and moving only its level is deliberate: it answers "what if my party were level 20" rather than "what would a level-20 player's completely different party be", and it is about ten times cheaper than re-ranking every attacker seven times. The Estimator itself is Pokebattler's definition, time to win including rejoin time divided by the raid timer.