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 3 to be safe — 2 if everyone is prepared

At level 40, a party of Rotom's top six counters needs 1.75 trainers (round up: 2), and a mixed lobby of ranks 13-24 needs 2.04 (round up: 3). The raid timer is 300 seconds and one prepared trainer alone would take 8:03. No level in this range makes it soloable with a prepared party. A duo works from level 30.

Rotom · Tier 5

electricghost

Weak to

groundghostdark

Boss CP: 32,310
Boss HP: 15,000
Raid timer: 300s
Party used: 6

Trainers needed, by attacker level

Scroll sideways for the mixed-lobby column.

Trainers needed to beat Rotom 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	3(2.03)	3(2.49)	3(2.98)	11:27	6.0
Level 25	2(1.81)	3(2.17)	3(2.53)	10:00	6.0
Level 30	2(1.65)	2(1.94)	3(2.24)	8:55	5.9
Level 35	2(1.52)	2(1.83)	3(2.15)	8:26	5.8
Level 40	2(1.42)	2(1.75)	3(2.04)	8:03	5.7
Level 45	2(1.38)	2(1.71)	2(1.95)	7:51	5.6
Level 50	2(1.33)	2(1.64)	2(1.89)	7:33	5.5

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.

2 trainers at level 40

Necrozma (Dawn Wings)1.42

A prepared party

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

2 trainers at level 40

Necrozma (Dawn Wings)1.42
Landorus (Therian)1.70
Darkrai1.78
Groudon1.80
Eternatus1.89
Lunala1.91

A mixed local group

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

3 trainers at level 40

Garchomp1.98
Hisuian Zoroark2.02
Chandelure2.02
Gholdengo2.01
Mamoswine2.03
Landorus (Incarnate)2.03

The party these numbers assume

1. Necrozma (Dawn Wings)

Psycho Cut + Moongeist Beam

2. Landorus (Therian)

Mud Shot + Sandsear Storm

3. Darkrai

Snarl + Foul Play

4. Groudon

Mud Shot + Precipice Blades

5. Eternatus

Dragon Tail + Dynamax Cannon

6. Lunala

Shadow Claw + Shadow Ball

See the full ranked counter list for Rotom · 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.