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 Walrein's top six counters needs 1.86 trainers (round up: 2), and a mixed lobby of ranks 13-24 needs 2.19 (round up: 3). The raid timer is 300 seconds and one prepared trainer alone would take 8:33. No level in this range makes it soloable with a prepared party. A duo works from level 35.

Walrein · Tier 5

icewater

Weak to

fightingrockgrasselectric

Boss CP: 33,344
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 Walrein 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(2.15)	3(2.91)	4(3.32)	13:23	6.0
Level 25	2(1.97)	3(2.42)	3(2.77)	11:07	6.0
Level 30	2(1.71)	3(2.10)	3(2.43)	9:40	6.0
Level 35	2(1.64)	2(1.96)	3(2.30)	9:03	6.0
Level 40	2(1.60)	2(1.86)	3(2.19)	8:33	6.0
Level 45	2(1.50)	2(1.77)	3(2.12)	8:08	6.0
Level 50	2(1.47)	2(1.71)	3(2.04)	7:52	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.

2 trainers at level 40

Keldeo1.60

A prepared party

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

2 trainers at level 40

Keldeo1.60
Kartana1.86
Terrakion1.89
Zeraora1.90
Lucario1.94
Blaziken1.97

A mixed local group

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

3 trainers at level 40

Hisuian Decidueye2.09
Urshifu (Single Strike)2.12
Zarude2.14
Rillaboom2.14
Conkeldurr2.16
Kyurem (Black)2.18

The party these numbers assume

1. Keldeo

Low Kick + Secret Sword

2. Kartana

Razor Leaf + Sacred Sword

3. Terrakion

Double Kick + Sacred Sword

4. Zeraora

Volt Switch + Plasma Fists

5. Lucario

Force Palm + Aura Sphere

6. Blaziken

Counter + Aura Sphere

See the full ranked counter list for Walrein · 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.