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 Gyarados's top six counters needs 3.81 trainers (round up: 4), and a mixed lobby of ranks 13-24 needs 4.39 (round up: 5). The raid timer is 300 seconds and one prepared trainer alone would take 17:42. No level in this range makes it soloable with a prepared party.

Mega Gyarados · Primal

waterdark

Weak to

fightingbuggrasselectricfairy

Boss CP: 74,538
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 Gyarados 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(4.58)	7(6.14)	7(6.74)	28:31	6.0
Level 25	4(3.90)	6(5.10)	6(5.66)	23:42	6.0
Level 30	4(3.65)	5(4.44)	5(4.85)	20:40	6.0
Level 35	4(3.47)	5(4.18)	5(4.60)	19:24	6.0
Level 40	4(3.12)	4(3.81)	5(4.39)	17:42	6.0
Level 45	4(3.04)	4(3.67)	5(4.22)	17:03	6.0
Level 50	3(2.96)	4(3.52)	5(4.07)	16:23	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.

4 trainers at level 40

Keldeo3.12

A prepared party

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

4 trainers at level 40

Keldeo3.12
Kartana3.68
Zeraora3.97
Xurkitree4.00
Regieleki4.01
Lucario4.05

A mixed local group

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

5 trainers at level 40

Zarude4.27
Rillaboom4.29
Urshifu (Rapid Strike)4.32
Hisuian Decidueye4.35
Urshifu (Single Strike)4.40
Raikou4.38

The party these numbers assume

1. Keldeo

Low Kick + Secret Sword

2. Kartana

Fury Cutter + Sacred Sword

3. Zeraora

Volt Switch + Plasma Fists

4. Xurkitree

Thunder Shock + Discharge

5. Regieleki

Lock-On + Thunder Cage

6. Lucario

Force Palm + Aura Sphere

See the full ranked counter list for Mega Gyarados · 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.