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 2 to be safe — 1 if everyone is prepared

At level 40, a party of Shellder's top six counters needs 0.97 trainers (round up: 1), and a mixed lobby of ranks 13-24 needs 1.20 (round up: 2). The raid timer is 180 seconds and one prepared trainer alone would take 2:50. A prepared solo becomes possible at level 40. A duo works from level 20.

Shellder · Shadow Tier 3

water

Weak to

grasselectric

Boss CP: 10,113
Boss HP: 4,000
Raid timer: 180s
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	2(1.35)	2(1.40)	2(1.69)	4:05	5.7
Level 25	2(1.17)	2(1.21)	2(1.48)	3:32	5.2
Level 30	2(1.03)	2(1.07)	2(1.32)	3:08	4.5
Level 35	1(0.96)	2(1.02)	2(1.26)	2:58	4.0
Level 40	1(0.89)	1(0.97)	2(1.20)	2:50	3.6
Level 45	1(0.86)	1(0.93)	2(1.16)	2:44	3.3
Level 50	1(0.83)	1(0.91)	2(1.12)	2:39	2.9

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.

1 trainer at level 40

Regieleki0.89

A prepared party

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

1 trainer at level 40

Regieleki0.89
Thundurus (Therian)0.98
Kartana0.97
Zeraora0.97
Xurkitree0.97
Zekrom1.03

A mixed local group

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

2 trainers at level 40

Meowscarada1.17
Raikou1.17
Roserade1.17
Kyurem (Black)1.18
Necrozma (Dawn Wings)1.19
Magnezone1.19

The party these numbers assume

1. Regieleki

Thunder Shock + Thunder Cage

2. Thundurus (Therian)

Volt Switch + Wildbolt Storm

3. Kartana

Razor Leaf + Leaf Blade

4. Zeraora

Spark + Plasma Fists

5. Xurkitree

Thunder Shock + Discharge

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.