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 5 to be safe — 4 if everyone is prepared

At level 40, a party of Mega Gengar's top six counters needs 3.32 trainers (round up: 4), and a mixed lobby of ranks 13-24 needs 4.14 (round up: 5). The raid timer is 300 seconds and one prepared trainer alone would take 15:25. No level in this range makes it soloable with a prepared party.

Mega Gengar · Primal

ghostpoison

Weak to

groundghostpsychicdark

Boss CP: 79,872
Boss HP: 22,500
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	5(4.51)	6(5.69)	7(6.26)	26:26	6.0
Level 25	4(3.77)	5(4.54)	6(5.23)	21:07	6.0
Level 30	4(3.40)	4(3.92)	5(4.68)	18:12	6.0
Level 35	4(3.17)	4(3.58)	5(4.42)	16:38	6.0
Level 40	3(3.00)	4(3.32)	5(4.14)	15:25	6.0
Level 45	3(2.95)	4(3.19)	4(3.93)	14:49	6.0
Level 50	3(2.92)	4(3.07)	4(3.80)	14:16	6.0

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.

3 trainers at level 40

Necrozma (Dawn Wings)3.00

A prepared party

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

4 trainers at level 40

Necrozma (Dawn Wings)3.00
Mewtwo3.21
Landorus (Therian)3.33
Hoopa (Unbound)3.35
Necrozma (Dusk Mane)3.48
Groudon3.53

A mixed local group

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

5 trainers at level 40

Metagross4.01
Hydreigon3.98
Yveltal4.02
Tyranitar4.04
Landorus (Incarnate)4.06
Lunala4.06

The party these numbers assume

1. Necrozma (Dawn Wings)

Psycho Cut + Moongeist Beam

2. Mewtwo

Psycho Cut + Psystrike

3. Landorus (Therian)

Mud Shot + Sandsear Storm

4. Hoopa (Unbound)

Confusion + Psychic

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.