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 4 to be safe — 3 if everyone is prepared

At level 40, a party of Arceus (Ghost)'s top six counters needs 2.58 trainers (round up: 3), and a mixed lobby of ranks 13-24 needs 3.04 (round up: 4). The raid timer is 300 seconds and one prepared trainer alone would take 11:51. No level in this range makes it soloable with a prepared party.

Arceus (Ghost) · Tier 5

ghost

Weak to

ghostdark

Boss CP: 49,286
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 Arceus (Ghost) 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(2.87)	4(3.92)	5(4.57)	18:02	6.0
Level 25	3(2.50)	4(3.23)	4(3.73)	14:51	6.0
Level 30	3(2.19)	3(2.90)	4(3.33)	13:22	6.0
Level 35	3(2.09)	3(2.78)	4(3.17)	12:47	6.0
Level 40	3(2.03)	3(2.58)	4(3.04)	11:51	6.0
Level 45	2(1.93)	3(2.49)	3(2.91)	11:28	6.0
Level 50	2(1.89)	3(2.42)	3(2.80)	11:09	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.

3 trainers at level 40

Necrozma (Dawn Wings)2.03

A prepared party

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

3 trainers at level 40

Necrozma (Dawn Wings)2.03
Darkrai2.66
Blacephalon2.64
Lunala2.67
Tyranitar2.72
Kyurem (Black)2.75

A mixed local group

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

4 trainers at level 40

Chandelure2.93
Zacian (Crowned Sword)2.99
Hoopa (Unbound)2.98
Zamazenta (Crowned Shield)2.98
Hoopa2.98
Eternatus2.98

The party these numbers assume

1. Necrozma (Dawn Wings)

Psycho Cut + Moongeist Beam

2. Darkrai

Snarl + Foul Play

3. Blacephalon

Astonish + Shadow Ball

4. Lunala

Shadow Claw + Shadow Ball

5. Tyranitar

Bite + Brutal Swing

6. Kyurem (Black)

Shadow Claw + Freeze Shock

See the full ranked counter list for Arceus (Ghost) · 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.