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 Greninja's top six counters needs 1.14 trainers (round up: 2), and a mixed lobby of ranks 13-24 needs 1.28 (round up: 2). The raid timer is 300 seconds and one prepared trainer alone would take 5:18. No level in this range makes it soloable with a prepared party. A duo works from level 20.

Mega Greninja · Mega

waterdark

Weak to

fightingbuggrasselectricfairy

Boss CP: 41,597
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 Greninja 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(1.34)	2(1.74)	2(1.93)	8:05	6.0
Level 25	2(1.19)	2(1.45)	2(1.67)	6:44	6.0
Level 30	2(1.05)	2(1.25)	2(1.44)	5:49	6.0
Level 35	2(1.01)	2(1.20)	2(1.37)	5:33	6.0
Level 40	1(0.96)	2(1.14)	2(1.28)	5:18	6.0
Level 45	1(0.94)	2(1.08)	2(1.24)	5:02	6.0
Level 50	1(0.87)	2(1.05)	2(1.19)	4:52	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.

1 trainer at level 40

Keldeo0.96

A prepared party

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

2 trainers at level 40

Keldeo0.96
Kartana1.12
Zeraora1.18
Zekrom1.19
Regieleki1.21
Lucario1.18

A mixed local group

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

2 trainers at level 40

Urshifu (Single Strike)1.27
Xurkitree1.23
Tapu Bulu1.28
Hisuian Decidueye1.29
Rillaboom1.27
Eternatus1.30

The party these numbers assume

1. Keldeo

Low Kick + Secret Sword

2. Kartana

Fury Cutter + Sacred Sword

3. Zeraora

Volt Switch + Plasma Fists

4. Zekrom

Charge Beam + Fusion Bolt

5. Regieleki

Thunder Shock + Thunder Cage

6. Lucario

Force Palm + Aura Sphere

See the full ranked counter list for Mega Greninja · 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.