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 — 3 if everyone is prepared

At level 40, a party of Shellder's top six counters needs 2.35 trainers (round up: 3), and a mixed lobby of ranks 13-24 needs 2.91 (round up: 3). The raid timer is 300 seconds and one prepared trainer alone would take 10:48. No level in this range makes it soloable with a prepared party.

Shellder · Elite

water

Weak to

grasselectric

Boss CP: 22,614
Boss HP: 20,000
Raid timer: 300s
Party used: 6

Trainers needed, by attacker level

Scroll sideways for the mixed-lobby column.

Trainers needed to beat Shellder 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	4(3.32)	4(3.38)	5(4.13)	15:33	6.0
Level 25	3(2.73)	3(2.88)	4(3.54)	13:14	6.0
Level 30	3(2.44)	3(2.57)	4(3.18)	11:51	5.9
Level 35	3(2.31)	3(2.45)	4(3.03)	11:18	5.8
Level 40	3(2.21)	3(2.35)	3(2.91)	10:48	5.8
Level 45	3(2.15)	3(2.27)	3(2.81)	10:27	5.7
Level 50	3(2.03)	3(2.17)	3(2.69)	9:59	5.6

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

Regieleki2.21

A prepared party

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

3 trainers at level 40

Regieleki2.21
Kartana2.34
Zeraora2.35
Xurkitree2.37
Thundurus (Therian)2.37
Zekrom2.44

A mixed local group

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

3 trainers at level 40

Kyurem (Black)2.80
Roserade2.81
Meowscarada2.83
Necrozma (Dawn Wings)2.86
Magnezone2.91
Breloom2.93

The party these numbers assume

1. Regieleki

Lock-On + Thunder Cage

2. Kartana

Razor Leaf + Leaf Blade

3. Zeraora

Volt Switch + Plasma Fists

4. Xurkitree

Thunder Shock + Discharge

5. Thundurus (Therian)

Volt Switch + Wildbolt Storm

6. Zekrom

Charge Beam + Fusion Bolt

See the full ranked counter list for Shellder · 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.