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 — 2 if everyone is prepared

At level 40, a party of Mega Gengar's top six counters needs 1.31 trainers (round up: 2), and a mixed lobby of ranks 13-24 needs 1.60 (round up: 2). The raid timer is 300 seconds and one prepared trainer alone would take 6:06. No level in this range makes it soloable with a prepared party. A duo works from level 25.

Mega Gengar · Mega

ghostpoison

Weak to

groundghostpsychicdark

Boss CP: 50,516
Boss HP: 9,000
Raid timer: 300s
Party used: 6

Trainers needed, by attacker level

Scroll sideways for the mixed-lobby column.

Trainers needed to beat Mega Gengar 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(1.82)	3(2.21)	3(2.52)	10:16	6.0
Level 25	2(1.46)	2(1.79)	3(2.04)	8:19	6.0
Level 30	2(1.32)	2(1.54)	2(1.80)	7:08	6.0
Level 35	2(1.19)	2(1.42)	2(1.71)	6:35	5.9
Level 40	2(1.18)	2(1.31)	2(1.60)	6:06	5.9
Level 45	2(1.16)	2(1.26)	2(1.54)	5:53	5.9
Level 50	2(1.12)	2(1.21)	2(1.48)	5:38	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

Necrozma (Dawn Wings)1.18

A prepared party

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

2 trainers at level 40

Necrozma (Dawn Wings)1.18
Landorus (Therian)1.30
Hoopa (Unbound)1.32
Mewtwo1.33
Necrozma (Dusk Mane)1.37
Groudon1.39

A mixed local group

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

2 trainers at level 40

Hisuian Zoroark1.53
Metagross1.56
Kyurem (Black)1.56
Garchomp1.59
Yveltal1.59
Salamence1.58

The party these numbers assume

1. Necrozma (Dawn Wings)

Psycho Cut + Moongeist Beam

2. Landorus (Therian)

Mud Shot + Sandsear Storm

3. Hoopa (Unbound)

Confusion + Psychic

4. Mewtwo

Psycho Cut + Psystrike

5. Necrozma (Dusk Mane)

Psycho Cut + Sunsteel Strike

6. Groudon

Mud Shot + Precipice Blades

See the full ranked counter list for Mega Gengar · 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.