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 Walrein's top six counters needs 0.62 trainers (round up: 1), and a mixed lobby of ranks 13-24 needs 0.74 (round up: 1). The raid timer is 180 seconds and one prepared trainer alone would take 1:49. A prepared solo becomes possible at level 20. A duo works from level 20.

Walrein · Tier 3

icewater

Weak to

fightingrockgrasselectric

Boss CP: 16,335
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 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	1(0.75)	1(0.93)	2(1.07)	2:44	5.7
Level 25	1(0.64)	1(0.79)	1(0.92)	2:19	5.3
Level 30	1(0.59)	1(0.70)	1(0.81)	2:02	4.7
Level 35	1(0.54)	1(0.65)	1(0.77)	1:54	4.2
Level 40	1(0.54)	1(0.62)	1(0.74)	1:49	3.9
Level 45	1(0.53)	1(0.59)	1(0.71)	1:44	3.6
Level 50	1(0.52)	1(0.58)	1(0.69)	1:42	3.4

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

Keldeo0.54

A prepared party

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

1 trainer at level 40

Keldeo0.54
Terrakion0.63
Lucario0.64
Kartana0.63
Zeraora0.65
Regieleki0.66

A mixed local group

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

1 trainer at level 40

Conkeldurr0.71
Urshifu (Single Strike)0.71
Zarude0.72
Raikou0.73
Rillaboom0.73
Kyurem (Black)0.74

The party these numbers assume

1. Keldeo

Low Kick + Secret Sword

2. Terrakion

Double Kick + Sacred Sword

3. Lucario

Force Palm + Aura Sphere

4. Kartana

Razor Leaf + Sacred Sword

5. Zeraora

Volt Switch + Plasma Fists

6. Regieleki

Thunder Shock + Thunder Cage

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.