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 1 to be safe — 1 if everyone is prepared

At level 40, a party of Chespin's top six counters needs 0.36 trainers (round up: 1), and a mixed lobby of ranks 13-24 needs 0.44 (round up: 1). The raid timer is 180 seconds and one prepared trainer alone would take 1:03. A prepared solo becomes possible at level 20. A duo works from level 20.

Chespin · Tier 3

grass

Weak to

flyingpoisonbugfireice

Boss CP: 8,250
Boss HP: 3,600
Raid timer: 180s
Party used: 6

Trainers needed, by attacker level

Scroll sideways for the mixed-lobby column.

Trainers needed to beat Chespin 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	1(0.45)	1(0.50)	1(0.60)	1:27	1.4
Level 25	1(0.38)	1(0.43)	1(0.53)	1:15	0.7
Level 30	1(0.35)	1(0.40)	1(0.49)	1:10	0.4
Level 35	1(0.35)	1(0.38)	1(0.46)	1:07	0.3
Level 40	1(0.34)	1(0.36)	1(0.44)	1:03	0.2
Level 45	1(0.31)	1(0.35)	1(0.43)	1:01	0.1
Level 50	1(0.29)	1(0.34)	1(0.42)	1:00	0.1

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.

1 trainer at level 40

Blacephalon0.34

A prepared party

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

1 trainer at level 40

Blacephalon0.34
Kyurem (White)0.34
Rayquaza0.35
Kyurem (Black)0.37
Eternatus0.37
Reshiram0.38

A mixed local group

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

1 trainer at level 40

Chandelure0.43
Cinderace0.43
Naganadel0.43
Toucannon0.44
Zacian (Crowned Sword)0.44
Blaziken0.44

The party these numbers assume

1. Blacephalon

Incinerate + Mind Blown

2. Kyurem (White)

Ice Fang + Ice Burn

3. Rayquaza

Air Slash + Dragon Ascent

4. Kyurem (Black)

Dragon Tail + Freeze Shock

5. Eternatus

Poison Jab + Dynamax Cannon

6. Reshiram

Fire Fang + Fusion Flare

See the full ranked counter list for Chespin · 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.