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 Magearna'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 180 seconds and one prepared trainer alone would take 2:17. A prepared solo becomes possible at level 25. A duo works from level 20.

Magearna · Tier 3

steelfairy

Weak to

groundfire

Boss CP: 24,260
Boss HP: 3,600
Raid timer: 180s
Party used: 6

Trainers needed, by attacker level

Scroll sideways for the mixed-lobby column.

Trainers needed to beat Magearna 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(0.86)	2(1.09)	2(1.29)	3:11	3.9
Level 25	1(0.76)	1(0.95)	2(1.13)	2:46	2.8
Level 30	1(0.69)	1(0.86)	2(1.03)	2:31	2.1
Level 35	1(0.66)	1(0.82)	1(0.98)	2:24	1.8
Level 40	1(0.65)	1(0.78)	1(0.94)	2:17	1.6
Level 45	1(0.62)	1(0.76)	1(0.92)	2:13	1.5
Level 50	1(0.60)	1(0.74)	1(0.88)	2:10	1.3

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

Blacephalon0.65

A prepared party

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

1 trainer at level 40

Blacephalon0.65
Reshiram0.75
Landorus (Therian)0.76
Chandelure0.83
Cinderace0.84
Volcarona0.86

A mixed local group

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

1 trainer at level 40

Delphox0.92
Moltres0.92
Entei0.93
Charizard0.94
Emboar0.94
Infernape0.94

The party these numbers assume

1. Blacephalon

Incinerate + Mind Blown

2. Reshiram

Fire Fang + Fusion Flare

3. Landorus (Therian)

Mud Shot + Sandsear Storm

4. Chandelure

Fire Spin + Overheat

5. Cinderace

Fire Spin + Pyroball

6. Volcarona

Fire Spin + Overheat

See the full ranked counter list for Magearna · 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.