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 Gastly's top six counters needs 0.78 trainers (round up: 1), and a mixed lobby of ranks 13-24 needs 0.94 (round up: 1). The raid timer is 300 seconds and one prepared trainer alone would take 3:36. A prepared solo becomes possible at level 25. A duo works from level 20.

Gastly · Tier 5

ghostpoison

Weak to

groundghostpsychicdark

Boss CP: 22,291
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 Gastly 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(0.98)	2(1.13)	2(1.39)	5:12	6.0
Level 25	1(0.79)	1(0.97)	2(1.20)	4:26	6.0
Level 30	1(0.73)	1(0.86)	2(1.04)	3:58	5.9
Level 35	1(0.71)	1(0.82)	1(0.99)	3:47	5.8
Level 40	1(0.67)	1(0.78)	1(0.94)	3:36	5.5
Level 45	1(0.64)	1(0.75)	1(0.91)	3:28	5.3
Level 50	1(0.60)	1(0.73)	1(0.88)	3:20	5.0

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

Necrozma (Dawn Wings)0.67

A prepared party

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

1 trainer at level 40

Necrozma (Dawn Wings)0.67
Mewtwo0.74
Hoopa (Unbound)0.77
Landorus (Therian)0.81
Darkrai0.83
Groudon0.87

A mixed local group

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

1 trainer at level 40

Tyranitar0.90
Zacian (Crowned Sword)0.92
Dragapult0.93
Absol0.93
Gholdengo0.94
Latios0.95

The party these numbers assume

1. Necrozma (Dawn Wings)

Psycho Cut + Moongeist Beam

2. Mewtwo

Psycho Cut + Psystrike

3. Hoopa (Unbound)

Confusion + Psychic

4. Landorus (Therian)

Mud Shot + Sandsear Storm

5. Darkrai

Snarl + Foul Play

6. Groudon

Mud Shot + Precipice Blades

See the full ranked counter list for Gastly · 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.